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Dissociative states and MS

30/04/2026 Gavin Giovannoni

This MS-related group of symptoms is probably neglected in routine MS neurological practice and may fall through the cracks.

Key points

Dissociative states in people with MS may arise for different reasons: organic (resulting from damage to the temporal and parietal lobes), psychogenic (following psychological trauma) or iatrogenic (induced by drug treatments).
Such states range from transient feelings of unreality to recurring episodes of depersonalisation and/or derealisation. Other presentations may also occur.
Depersonalisation feels like being detached from one’s own body or thoughts, feeling like an ‘outside observer’ of one’s life.
Derealisation feels like being detached from the external world, which may appear foggy, dreamlike, lifeless or two-dimensional.
In MS, dissociation often has a physical (organic) basis in the brain. This article explores the specific effects of damage to each of the four lobes of the human brain.
Managing dissociative states in MS requires a dual approach: biological (treating the underlying MS disease) and psychological.
To differentiate between physical and psychological causes, doctors must consider the possibility of an MS relapse, an infection or the effects of an MS-related treatment. Checks for balance, hearing and psychological screening are also needed.

Causes and range of dissociative states

People with MS have an elevated risk of experiencing dissociative phenomena that give rise to alterations of consciousness, self-perception and reality testing (being able to assess what is real versus what is imagined). These dissociative states − ranging from transient feelings of unreality to chronic depersonalisation−derealisation disorder (DPDR) and non-epileptic seizures − are often undiagnosed. They may arise for different reasons.

Organic dissociation results from damage(lesions)to the temporal and parietal lobes, which can disrupt neural networks responsible for ‘embodied self-awareness’ (the constant experience of oneself through physical sensations, emotions and bodily signals).
Psychogenic dissociative states can occur in people with MS following the psychological trauma of diagnosis and the high prevalence of comorbid post-traumatic stress disorder (PTSD).
Iatrogenic dissociative states can be induced by drug treatments, particularly high-dose corticosteroids and psychoactive symptomatic treatments.

Dissociation is typically characterised by disruption in the normal integration of consciousness, memory, identity, emotion, perception, body representation, motor control and behaviour. The most frequently reported dissociative symptoms in the MS population fall under the spectrum of depersonalisation−derealisation.

Depersonalisation (the fragmentation of self)

Depersonalisation is characterised by a persistent or recurring feeling of being detached from one’s own body or thoughts. People with MS describe this as feeling like an ‘outside observer’ of their life, like watching oneself in a movie, or like a ‘robot’ with no control over their speech or actions. In MS, depersonalisation is associated with damage to the parietal lobe or the spinal cord – areas that help the brain detect body position and movement (proprioception). People with damage to these areas may feel as though a limb does not belong to them. This is not a delusion, because the person may see their limb move and intellectually know it is theirs. Rather, it is a sensory problem with the ‘body schema’ (the brain’s internal map of your body), that no longer matches your physical body.

Derealisation (the distortion of the world)

Derealisation involves a feeling of being detached from your surroundings. The external world may appear foggy, dreamlike, lifeless, colourless or artificially two-dimensional. Objects may appear distorted in size or shape; sounds may seem muted or distant. Derealisation is often worsened by sensory problems in people with MS (affecting sight, sound, touch, taste, smell or movement). Optic neuritis, a common early sign of MS, causes visual blurring, reduced colour intensity and visual field defects (gaps); see Colour vision and Driving at night. When the brain receives unclear visual input, it struggles to construct a vivid, real-feeling model of the environment, which can lead to a secondary sense of derealisation.

Problems with balance (vestibular dysfunction, leading to vertigo, dizziness and gait instability) are often associated with derealisation; conflicting signals from the eyes and inner ear can cause people with MS to feel disoriented.

Non-epileptic seizures

Non-epileptic seizures, also referred to as dissociative seizures, resemble epileptic seizures − involving convulsive movements, apparent loss of consciousness and stiffening of the body. However, they are not caused by abnormal electrical activity in the brain (usually visible on an electroencephalogram) but are psychological, most likely a mechanism for managing distress or trauma. Care is needed to determine the correct cause in each individual because people with MS are actually at increased risk for epilepsy due to brain lesions. Studies of magnetic resonance imaging (MRI) scans suggest that damage in the right brain hemisphere or the frontal lobes may increase the risk of non-epileptic seizures.

Dissociative amnesia and brain fog

Dissociative amnesia is the inability to recall important personal information, far beyond ordinary forgetting. It is usually related to stress or trauma. In MS, this poses a diagnostic challenge because many patients already experience cognitive dysfunction that affects processing speed and working memory. A study differentiating organic (‘true’) memory loss from dissociative amnesia in MS found that people who reported memory problems often had high levels of dissociation and anxiety but did not show major problems on formal memory testing.¹ This implies that the ‘memory loss’ experienced by many people with MS may be an attention problem due to a mild dissociative state or emotional overload, rather than a result of permanent damage to memory structures in the brain.

Dissociative identity disorder

While rare, cases of dissociative identity disorder (DID) have been reported in people with MS. DID is characterised by the presence of two or more distinct personality states. Affected individuals typically have experienced childhood trauma, which makes them more prone to develop dissociation. A diagnosis of MS acts as a further stressor that challenges their sense of identity. Other symptoms of DID may include physical weakness and sensory loss, which can mimic an MS relapse and lead to misdiagnosis.

Underlying disease processes in MS

In the general psychiatric population, dissociative disorders are usually regarded as psychological in origin. In MS, however, dissociation often has a physical basis in the brain. MS damages myelin (the protective covering of nerve fibres), severs nerve connections and affects grey matter, all of which disrupts communication between different brain regions. When these connections are broken, the brain cannot integrate sensation, emotion and thought into a conscious experience.

Structure of the brain, showing the left and right cerebral hemispheres (left) and the four lobes (frontal, parietal, temporal and occipital; right) in each cerebral hemisphere. Each individual lobe has particular key roles; however, they do not function in isolation but as part of a wider system of neural networks. From Gemini Pro.

Temporal lobe

The temporal lobes play a central role in processing memory and emotions as well as in combining auditory and visual information. MS-related damage in these areas is associated with psychiatric symptoms, including psychosis and dissociation. The temporal lobe also houses the limbic system, comprising the amygdala (which processes emotion) and the hippocampus (which supports memory). If there is damage to the white matter pathways between the limbic system and the frontal cortex (a region known as the uncinate fasciculus) or to sensory regions, the emotional content of experiences can be lost. For example, when a person with MS sees a familiar object or person, the visual cortex sends information to the limbic system, thus activating the appropriate emotional response (e.g. warmth, recognition). If MS disrupts this connection, the person may recognise the object but feel no emotional familiarity. This mismatch, i.e. recognition without feeling, is central to derealisation and to the jamais vu phenomenon (the strange feeling that something familiar is suddenly unfamiliar or new) that is often reported in temporal lobe disorders.

A sagittal (longitudinal) view of the human brain showing the interconnected network of the limbic system, a key regulator of emotion, memory and spatial navigation. From Gemini Pro 3.0.

Temporal lobe epilepsy

MS lesions in the temporal lobe can sometimes trigger epileptic activity. Even in the absence of full-blown convulsions, abnormal electrical activity there can cause ‘dreamy states,’ profound déjà vu or feelings of unreality similar to the warning phase (aura) of temporal lobe epilepsy. Symptoms of depersonalisation disorder overlap with those experienced in temporal lobe epilepsy, particularly unusual body experiences and memory distortions.

Parietal lobe

The parietal lobe combines sensory information from different sources to form a single perception (cognition) and helps the brain build a map of the body and the world around us. The brain constantly updates this map, or ‘body schema’, using signals from the spinal cord. MS lesions in the parietal lobe or spinal cord can interrupt this information and deprive the brain of body map data.

When the brain ceases to receive reliable input from a limb, because of MS-related damage, it may ‘dissociate’ that body part from its self-image. This can manifest as:

asomatognosia (the inability to recognise a part of one’s own body)
somatoparaphrenia (the delusion that a limb belongs to someone else)
depersonalisation (see above).

Temporoparietal junction

The temporoparietal junction, where the temporal and parietal lobes meet, is a hub for integrating balance, visual and somatosensory signals to locate the ‘self’ in space. Electrical stimulation of this area can cause out-of-body experiences. In MS, lesions affecting the temporoparietal junction or the balance pathways in the brainstem can trigger dissociative events (for example, a feeling of floating above one’s body or viewing oneself from outside. These episodes are often linked to balance problems, suggesting that the brain is trying to make sense of conflicting signals.

Occipital lobe

The occipital lobe is the main visual processing centre of the brain. Damage in this region or in visual pathways can lead to complex visual distortions that trigger derealisation. ‘Alice in Wonderland Syndrome’ is a perceptual distortion in which objects appear much smaller (micropsia) or much larger (macropsia) than they really are. When damage from MS affects the visual association areas, vision may appear two-dimensional, with the world looking ‘flat’ or like a painted backdrop. This loss of depth perception contributes to the feeling of living in a movie or a simulation.

Clinico-radiological paradox

The clinico-radiological paradox refers to the discrepancy between the number and volume of MS lesions seen on MRI and a patient’s level of physical disability. Some people with MS have extensive brain lesions but relatively normal movement and minimal disability scores. While these patients may appear physically ‘fine’, lesions in high-level areas of the cortex (frontal, parietal and temporal lobes) can disrupt cognitive and emotional networks. Such individuals may be at high risk for subjective dissociation − feeling fragmented or cognitively detached − while objective observers (and disability scales) fail to register any deficit. These hidden symptoms can worsen the patient’s sense of isolation and unreality.

Trauma-related causes

Receiving a diagnosis of MS

While localised MS lesions create the ‘hardware failure’ in the brain that enables dissociation, psychological factors often provide the ‘software trigger’. Receiving a diagnosis of MS may be considered a medical trauma, often involving invasive procedures (lumbar punctures), frightening MRI experiences (claustrophobia) and hospitalisations. These repeated exposures to threat and a feeling of helplessness and vulnerability can induce a state of chronic hyperarousal and subsequent dissociation, consistent with the dissociative subtype of PTSD. Many people with MS meet the diagnostic criteria for PTSD specifically related to their MS diagnosis and outlook (please see, How common is post-traumatic stress disorder in people with MS?). Developing an ongoing, incurable and potentially disabling neurological condition can shatter one’s expectations for the future. By detaching from the reality of their diagnosis, people with MS may attempt to shield themselves from overwhelming anxiety and grief. Dissociation serves as an adaptive defence mechanism – a ‘mental flight’ when physical flight is impossible. This sounds dramatic, but it may explain why some people with MS develop dissociative disorders.

Childhood trauma

Research has demonstrated a potential relationship between childhood trauma, dissociation and the development of MS. Severe stress, neglect or abuse in childhood permanently dysregulates the hypothalamic−pituitary−adrenal axis (a system that is crucial for the body’s stress management). It consists of three organs that each release hormones to eventually raise cortisol levels in the body. This results in a chronic proinflammatory state and altered cortisol responses, which may increase biological susceptibility to developing MS later in life. Large-scale cohort studies indicate that women who experienced childhood abuse are significantly more likely to develop MS in the future.²

Treatment-related causes

The management of MS involves disease-modifying therapies (DMTs) and corticosteroids for acute relapse management. Many of these agents have significant neuropsychiatric side effects that can mimic, induce or exacerbate dissociative states.

Corticosteroids. High doses of the intravenous corticosteroid methylprednisolone (e.g. 1000 mg daily for 3−5 days) are the standard of care for speeding up the recovery from acute MS relapses. It is known to cause acute psychiatric adverse effects in many patients (dependent on the corticosteroid dose).Symptoms often begin with insomnia and euphoria but can progress to severe mood lability, anxiety and frank dissociation and delirium. Patients may experience a ‘steroid high’ followed by a crash into depression; some develop acute psychosis with hallucinations and confusion. Corticosteroids enhance dopamine activity. They may cause acute, reversible reductions in hippocampal volume. Their effect on the brain presumably decouples the patient from reality, leading to a temporary dissociative or psychotic state that resolves upon tapering the steroid dosage.

Interferon-beta has a longstanding association with depression and anxiety. Interferons are cytokines that induce a proinflammatory response similar to ‘sickness behaviour,’ which includes social withdrawal, fatigue and anhedonia (inability to feel pleasure in activities that are usually considered to be pleasurable). They may also decrease serotonin levels in the brain.While direct dissociation is less common, the severe anxiety and depression induced by interferons presumably lower the threshold for the onset of stress-induced depersonalisation.

Natalizumab is a highly effective monoclonal antibody, but it carries specific risks. The ‘wearing off’ effect in the week preceding the next infusion can be characterised by intensifying fatigue, cognitive fog and mood instability, which may manifest as a feeling of detachment or unreality.The most severe risk associated with natalizumab is progressive multifocal leukoencephalopathy; this causes extensive, rapid demyelination that can lead to confusion, personality changes and cognitive decline. These symptoms can be misinterpreted as psychiatric dissociation or dementia in the early stages.

Fingolimod, an S1P modulator, has been associated with posterior reversible encephalopathy syndrome. This condition involves swelling in the posterior brain regions (parietal/occipital lobes) caused by leakage of fluid from capillaries. It presents with acute confusion, visual changes, headaches and altered consciousness − a constellation of symptoms that could mimic derealisation and dissociation.

Symptomatic treatments. Abrupt withdrawal of baclofen and tizanidine, which are used for spasticity, can cause severe delirium, hallucinations and dissociation. Similarly, gabapentin and pregabalin, which are often used in people with MS to manage neuropathic pain, can cause sedation and cognitive clouding (‘zombie-like’ feeling) that contribute to depersonalisation.

Diagnosis

When someone with MS develops dissociative symptoms, doctors must first rule out physical (organic) causes before assuming the problem is purely psychological. A diagnostic algorithm should do the following.

1. Rule out an MS relapse
Any new onset of psychiatric or dissociative symptoms warrants an MRI scan with gadolinium. New lesions in the temporal, parietal or frontal lobes can directly cause these symptoms.

2. Rule out infection
Urinary tract infections are extremely common in MS and are the leading cause of acute confusional states (delirium) that can mimic dissociation. A urinalysis and a workup for other infections are mandatory.

3. Review medication
Assess for recent steroid use, cumulative damage from anticholinergic drugs (e.g. for bladder dysfunction) or withdrawal from muscle relaxants (baclofen and tizanidine).

4. Check balance and hearing
‘Neuro-otological examination’ is a specialised assessment for dizziness, vertigo, hearing loss and balance disorders. Checking for nystagmus (uncontrollable eye movements) helps to diagnose balance disorders. Treating vertigo may resolve the derealisation.

5. Carry out psychological screening
Your health professional can use the Dissociative Experiences Scale (DES-II) or the Dissociative Disorders Interview Schedule to quantify symptom severity. People with MS generally score in the normal range on DES-II unless they have comorbid DID or PTSD.

Differentiating organic from psychiatric dissociation is difficult. It may require referral to a neuropsychiatrist. MS-related brain fog or cognitive impairment with an organic basis is characterised by slowed processing speed, word-finding difficulties and fatigue. Patients try to engage but fail. In comparison, psychiatric dissociation is characterised by a subjective sense of detachment (‘I am not here’). Patients may have preserved processing speed but feel emotionally disconnected. As noted above, MS cog-fog often contains a dissociative component driven by anxiety. Treating the anxiety usually clears the ‘cog-fog’ more effectively than cognitive rehabilitation alone.

Management

Managing dissociative states in MS requires a dual approach: biological (i.e. treating the underlying MS disease) and psychological.

Drug treatments

The primary prevention of organic dissociation involves preventing new lesion formation. High-efficacy DMTs are the best way to preserve brain volume and connectivity. Psychotropics such as selective serotonin reuptake inhibitors (e.g. fluoxetine, sertraline) can help manage the anxiety and depression that underlie DPDR. They may also help with MS-related fatigue. Antipsychotics (e.g. quetiapine, olanzapine) may be rarely indicated for managing steroid-induced psychosis or organic paranoia related to temporal lobe lesions. Lamotrigine and other anticonvulsants (e.g. carbamazepine and oxcarbazepine) can be used to treat both seizures and depersonalisation; they are particularly beneficial in patients with temporal lobe pathology.

Psychological interventions

Cognitive behavioural therapy is the gold standard for treating DPDR. It helps patients reframe the terrifying sensation of ‘going crazy’ or ‘disappearing’ as a harmless (albeit distressing) symptom of anxiety or the disease. This reduces the catastrophic thinking that perpetuates the dissociation.

Eye movement desensitisation and reprocessing (EMDR) can be effective for MS-related PTSD (medical trauma) or childhood trauma. However, standard EMDR can be overwhelming for patients with dissociation. Modified (e.g. ‘titrated’) EMDR protocols can prevent flooding the patient with traumatic memories before they have stabilisation skills. EMDR is available via some UK NHS psychiatric services.

Grounding and mindfulness techniques (e.g. holding an ice cube, describing the environment) anchor the patient in the present moment and help them to manage acute episodes of derealisation. Mindfulness-based stress reduction has shown efficacy in improving the quality of life and reducing depressive symptoms in people with MS.

Vestibular rehabilitation therapy (VRT) is a specialised, exercise-based physical therapy designed to reduce vertigo, dizziness and imbalance. It should be offered to people with MS where derealisation is driven by vertigo. VRT helps the brain compensate for inner-ear deficits through personalised exercises that focus on gaze stabilisation, balance training and habituation. Physical therapy to improve balance and gaze stability can directly reduce the feeling of unreality.

Conclusions

To self-manage dissociative states effectively, individuals with MS can proactively apply several key principles highlighted above. During acute episodes of derealisation or dissociation, employing practical grounding and mindfulness techniques – such as holding an ice cube or actively describing the immediate environment – can serve as vital tools to anchor oneself in the present moment. Furthermore, individuals can apply cognitive behavioural principles by ‘reframing’ their experiences. Recognising that terrifying feelings of ‘disappearing’ or ‘going crazy’ are often harmless symptoms of anxiety or the disease itself can help reduce the catastrophic thinking that perpetuates dissociation.

Effective self-management also involves staying vigilant about physical triggers (e.g. monitoring for signs of urinary tract infections or medication side effects) and pursuing targeted physical interventions, such as vestibular rehabilitation exercises, if feelings of unreality are driven by dizziness and balance issues. By combining these practical coping strategies with a clear understanding of the biological and psychological origins of their symptoms, individuals with MS can regain a sense of control and significantly reduce the impact of dissociative states on their daily lives.

References

Bruce J, et al. Self-reported memory problems in multiple sclerosis: influence of psychiatric status and normative dissociative experiences. Arch Clin Neuropsychol 2010;25:39–48.
Rehan ST, et al. Association of adverse childhood experiences with adulthood multiple sclerosis: A systematic review of observational studies. Brain Behav 2023;13:e3024.

DMTsDetail

S1P modulators

30/05/2023 Gavin Giovannoni

Summary

‘S1P modulators’ is the ‘short-hand’ we use to describe a group of drugs called sphingosine 1-phosphate receptor modulators (see Mode of action below). Fingolimod was the first of the S1P modulators to be licensed in MS (in 2010) and the first oral tablet approved for use in MS. Since then, three more S1P modulators have been licensed: siponimod, ozanimod and ponesimod. These are highly effective drugs, decreasing the relapse rate by over 50%, reducing worsening disability and the development of new lesions on magnetic resonance imaging (MRI), and slowing the loss of brain volume. S1P modulators work by trapping lymphocytes in lymph nodes and causing a low lymphocyte count in virtually all people with MS on the drugs. These drugs are maintenance therapies taken continuously and hence cause systemic immunosuppression. As a result, S1P modulators are associated with rare opportunistic infections and secondary malignancies, for example, lymphomas and skin cancers. They are anti-trafficking drugs, i.e. they block lymphocytes migrating into the CNS of people with MS, so when they are stopped, they are associated with rebound disease activity. Rebound typically occurs at around 6 ̶ 8 weeks after stopping fingolimod and siponimod and may also occur with ozanimod and ponesimod. S1P modulators have off-target side effects; for example, they slow the heart rate down and may need to be started in a hospital or under observation.

Trade names

Gilenya (fingolimod), Mayzent (siponimod), Zeposia (ozanimod), Ponvory (ponesimod).

Mode of action

Fingolimod is a sphingosine 1-phosphate (S1P) receptor modulator. Fingolimod is converted to an active drug, fingolimod phosphate, in the body. Fingolimod phosphate binds to its receptor (the S1P receptor) subtype 1 located on lymphocytes, which causes the receptors to be internalised and removed from the surface of the cells. By preventing S1P receptors from recirculating onto the surface of lymphocytes, fingolimod blocks the capacity of lymphocytes to leave lymph nodes, causing their redistribution rather than depletion. Siponimod, ozanimod and ponesimod are active drugs and do not need to be phosphorylated, but they work in the same way as fingolimod.

Efficacy

High; fingolimod is licensed in the UK and Europe as a second-line therapy for people with highly active MS. In other countries, fingolimod can be used first-line. Siponimod is licensed for people with MS with active secondary progressive MS. Ozanimod and ponesimod are licensed as first-line treatments for people with active MS.

Class

Maintenance, immunosuppressive.

Immunosuppression

Yes, systemic.

Dosing

Fingolimod dosing

In adults, the recommended dose of fingolimod is one 0.5 mg capsule taken orally once daily. In children with MS (10 years of age and above), the recommended dose is dependent on body weight:

body weight ≤40 kg: one 0.25 mg capsule taken orally once daily
body weight >40 kg: one 0.5 mg capsule taken orally once daily.

When people with MS start on 0.25 mg capsules and reach a stable body weight above 40 kg, they should be switched to 0.5 mg capsules. Fingolimod can be taken with or without food. Fingolimod capsules should always be swallowed intact without opening them.

Although the Gilenya SmPC states that when switching from a 0.25 mg to a 0.5 mg daily dose it is recommended to repeat the same first dose monitoring as for treatment initiation, we have not done this. The following text is from the Gilenya SmPC:

The same first dose monitoring as for treatment initiation is recommended when treatment is interrupted for:

1 day or more during the first 2 weeks of treatment
more than 7 days during weeks 3 and 4 of treatment
more than 2 weeks after one month of treatment.

If the treatment interruption is of a shorter duration than the above, the treatment should be continued with the next dose as planned.

Siponimod dosing

The dose of siponimod depends on how rapidly you can metabolise the drug. Before starting treatment, people with MS must be genotyped to determine their metaboliser status. In people with MS who metabolise the drug slowly and have the so-called 3-3 genotype, siponimod should not be used. In intermediate metabolisers (genotype 2-3 or 1-3), the recommended maintenance dose is 1 mg taken once daily (four tablets of 0.25 mg). In people with all other genotypes who are rapid metabolisers, the dose of siponimod is 2 mg per day.

To reduce off-target side effects, siponimod treatment is started with a titration pack that lasts for 5 days, as follows:

days 1 and 2: 0.25 mg once daily
day 3: 0.5 mg once daily
day 4: 0.75 mg once daily
day 5: 1.25 mg once daily
day 6: increase to the patient’s prescribed maintenance dose of siponimod.

During the first 6 days of treatment initiation, the recommended once-daily dose should be taken in the morning with or without food (see SmPC for more details).

Ozanimod dosing

The recommended dose is 0.92 mg of ozanimod once daily. To reduce off-target side effects, an initial dose titration is required over the first 7 days (see SmPC for more details):

days 1 ̶ 4: 0.23 mg once daily
days 5 ̶ 7: 0.46 mg once daily
day 8 onwards: 0.92 mg once daily.

Ponesimod dosing

The recommended dose is 20 mg of ponesimod once daily. To reduce off-target side effects, an initial dose titration is required over the first 14 days. The dose starts at 2 mg per day and builds up over 14 days to the maintenance dose of 20 mg per day (see SmPC for specific details).

Dose reduction

The European Medicines Agency recommends that if someone with MS has a persistent lymphopaenia of below 200/mm³ (grade 4), then S1P modulators should be stopped until the lymphocyte counts recover. It is our practice to put these patients on alternate-day dosing or to reduce the daily dose and to rechallenge them with the full dose once the counts have recovered to above 200/mm³. Now that fingolimod has been licensed for treating children with MS, with a dose based on weight, a 0.25 mg tablet is available. So instead of taking 0.5 mg on alternate days, there is also the possibility of taking 0.25 mg daily.

As the response to fingolimod or other S1P modulators and the risk of opportunistic infections are unrelated to the lymphocyte counts, the US Food and Drug Administration has not recommended routine monitoring of lymphocyte counts. Because of this, I am not unduly concerned about lymphocyte counts in patients on fingolimod and other S1P modulators and tend only to respond to counts of less than 100/mm³.

Main adverse events of special interest

Cardiac

The main adverse event of S1P modulators is a transient slowing of the heart rate that can, rarely, be associated with a heart block. This is why fingolimod is started in hospital with cardiac monitoring. With the newer generation S1P modulators, this is managed by a dose titration. Cardiac conduction abnormalities are usually transient and asymptomatic. Owing to the cardiac side effects, concurrent therapy with beta-blockers, heart-rate-lowering calcium channel blockers (such as verapamil or diltiazem), or other substances which may decrease heart rate (e.g. ivabradine, digoxin, anticholinesterase inhibitors or pilocarpine) is not recommended. The effects on heart rate and cardiac conduction may recur on the reintroduction of S1P modulator treatment, depending on the duration of the interruption and the time since the start of treatment. S1P modulators may prolong the so-called QT interval on your ECG, so they are best avoided in individuals with relevant risk factors, for example, low potassium or congenital QT prolongation.

Immunosuppressive effects

S1P modulators predispose people with MS to an infection risk, including opportunistic infections, and increase the risk of developing lymphomas and other malignancies, particularly those of the skin. Potential opportunistic infections include fungal infections, for example, cryptococcal meningitis and progressive multifocal leukoencephalopathy (PML). Before initiating treatment with S1P modulators, it is important to do a baseline infection screen and to check the full blood count. You must have antibodies or immunity to varicella (chickenpox) prior to starting treatment. If you are varicella negative, it is recommended that you receive a full course of one of the varicella vaccines. Similarly, you must have a full vaccine review before starting this class of treatment. Human papillomavirus (HPV) infection, including papilloma, dysplasia, warts and HPV-related cancers, has been reported in people with MS on S1P modulators, which is why we recommend cervical smears or HPV testing at baseline before starting treatment.

Macular oedema

Swelling of the macula, the central part of the retina, occurs in ~ 1 in 200 people with MS treated with fingolimod or another S1P modulator. This can cause symptoms and can be detected using the so-called Amsler grid (see below). You must be assessed at an eye clinic 3 ̶ 4 months after initiating an S1P modulator to screen for this complication. Some clinicians do baseline testing of the eye before initiating S1P modulators; in fact, this is in the SmPC for ponesimod. Please note that if you have a history of uveitis (inflammation in the eye) or have diabetes mellitus, you are at increased risk of developing macular oedema. I tend to avoid prescribing S1P modulators to patients with diabetes.

The Amsler grid (left) is a simple square containing a grid pattern and a dot in the middle. If there are problem spots in your field of vision, areas of the grid may appear blank or distorted (right, example).

Liver

Increased liver enzymes have been reported in people with MS on S1P modulators such as fingolimod. This is why your LFTs (liver function tests) are monitored after starting fingolimod and other S1P modulators, and if they exceed five times the upper limit of normal fingolimod needs to be stopped. LFTs are recommended at 1, 3, 6, 9 and 12 months after therapy and then 6 monthly after that. Please be aware that if you develop any symptoms suggestive of liver problems, such as unexplained nausea, vomiting, abdominal pain, fatigue, loss of appetite, or jaundice and/or dark urine, you should have liver enzymes checked. If you have pre-existing liver disease, most neurologists will avoid using this class of therapy.

High blood pressure

S1P modulators increase your blood pressure by a small amount. If you develop hypertension, you may need to start antihypertensive medications; hypertension occurs in ~ 1 in 20 people with MS treated with fingolimod and is less common with the newer generation S1P modulators.

Respiratory effects

S1P modulators cause a minor reduction in lung function, so neurologists tend to avoid using fingolimod and other S1P modulators in people with MS with pre-existing lung disease.

Vascular effects

Rare cases of posterior reversible encephalopathy syndrome (PRES) have been reported on S1P modulators. Symptoms can include sudden onset of severe headache, nausea, vomiting, altered mental status, visual disturbances and seizures. If you suspect you have PRES, you should contact your doctor urgently.

Cutaneous neoplasms

Basal cell carcinoma (BCC) and other cutaneous neoplasms, including malignant melanoma, squamous cell carcinoma, Kaposi’s sarcoma and Merkel cell carcinoma, have all been reported in people with MS on fingolimod, and there is the potential for these conditions to occur with the other S1P modulators. Please be vigilant for any new skin lesions and bring them to the attention of your doctor, who may need to refer you to a dermatologist. In our centre, we encourage our patients to take pictures of lesions with their smartphone camera and email them to us. We often get back a dermatology opinion very quickly this way. In people with MS at high risk, i.e. those with a dysplastic naevus syndrome, severe sun damage and/or prior history of skin cancer, we refer to dermatology for regular (annual) skin cancer screening. At present, annual skin screening is not justified in low-risk patients. Owing to the potential risk of malignant skin lesions, you need to be careful with excessive sunlight exposure or phototherapy with UV-B-radiation or PUVA-photochemotherapy.

Rebound disease activity

Severe exacerbation of disease has been observed in people with MS stopping fingolimod and siponimod treatment and may also occur with ozanimod and ponesimod. The possibility of recurrence of exceptionally high disease activity needs to be carefully considered when deciding on the sequence of treatments. Rebound typically occurs 6 ̶ 8 weeks after stopping fingolimod, siponimod and ozanimod. If it occurs with ponesimod, it will likely happen much earlier because ponesimod washes out more rapidly than the other S1P modulators.

Neutralising antibodies (NAbs)

NAbs are not a problem with S1P modulators because these DMTs are all small molecules and not a biological (protein) therapy.

Pharmacovigilance monitoring requirements

Baseline

Full blood count, urea and electrolytes, liver function tests, thyroid function tests, serum immunoglobulin levels, serology (varicella zoster virus, human immunodeficiency virus 1 and 2, hepatitis B and C, syphilis), tuberculosis enzyme-linked immune absorbent spot (TB ELISpot), up-to-date cervical smear and/or human papillomavirus testing, pregnancy test, blood pressure and electrocardiogram. Lung function tests are recommended for anyone with a history of asthma or lung disease.

Follow-up

FBC, LFTs and blood pressure should be monitored at months 1, 3, 6, 9 and 12 on therapy and 6-monthly thereafter.

Visual function

Macular oedema screening should be done 3 ̶ 4 months after treatment start in an eye clinic. The SmPC for ponesimod recommends a baseline eye scan, but this may not be necessary in people with low-risk MS.

Self-monitoring

All people with MS should be warned about opportunistic infections and informed to look out for symptoms suggestive of infections, suspicious skin lesions and symptoms of liver dysfunction. Women should be reminded to self-examine their breasts monthly and should have cervical smears and/or HPV testing done every 3 years. People with MS need to be aware of visual symptoms and can self-assess their macular function with an Amsler grid. There are several Amsler grid apps available for smartphones. Routine blood pressures also need to be taken.

Rebaselining

A rebaseline MRI scan needs to be done after the S1P modulator has had sufficient time to work. As S1P modulators work quite rapidly, I would recommend that an MRI is done 3 ̶ 6 months after starting treatment and that Gd-enhancement is included as part of the rebaselining MRI.

Women of childbearing potential and pregnancy

If you are a woman of childbearing age, before starting S1P modulator treatment, I would recommend a negative pregnancy test result. S1P modulators are potentially teratogenic, i.e. they can cause birth defects, therefore, you must have effective contraception whilst on treatment. It takes approximately 2 months to eliminate fingolimod from the body and 3 months to eliminate ozanimod; for ponesimod and siponimod, the elimination times are 1 week and 10 days, respectively. Therefore, on stopping treatment the potential risk to the foetus may persist and contraception should be continued during the drug elimination period. If you do fall pregnant whilst on an S1P modulator, we would not automatically recommend termination of pregnancy but, rather, refer you to a high-risk antenatal clinic for counselling and foetal screening. Many babies exposed to S1P modulators in the uterus have been born without any overt problems.

Breastfeeding

S1P modulators are excreted in the breast milk of lactating women and have the potential for serious adverse reactions in nursing infants, so women on these drugs should not breastfeed.

Fertility

I am not aware of any data to suggest that S1P modulators are associated with reduced female fertility.

Male fertility

S1P modulators have not been shown to affect sperm counts or sperm motility. There is no need for men with MS to stop fingolimod if they want to father a child.

Vaccination

It is safe to receive component or inactivated vaccines, but the antibody responses may be blunted. Live vaccines are contraindicated in people with MS on S1P modulators. Live viruses, particularly ones that can infect the central nervous system, are potentially dangerous.

Travel

People with MS need to be aware that being on an S1P modulator may affect travel; for example, some countries require you to be vaccinated against yellow fever, which involves a live attenuated vaccine and is hence contraindicated. If you travel to places associated with exotic infections, for example, dengue fever, you may be at risk of complications from these infections because S1P modulators are immunosuppressive.

Summaries of Product Characteristics (SmPC)

Gilenya, Mayzent, Zeposia, Ponvory.

Switching to an S1P modulator

Interferon and glatiramer acetate

In general, S1P modulators can be started immediately after discontinuation of interferon or glatiramer acetate. It is important that all the recommended baseline screening tests and vaccination reviews are done before starting S1P modulators.

SIP modulator to S1P modulator switch

In general, switching from one S1P modulator to another is possible. I would recommend rechecking baseline investigations before making the switch and ensuring a 4-week washout with fingolimod, siponimod and ozanimod prior to starting the new agent. With ponesimod, I limit the washout to 7 days. Overlapping the washout of one S1P modulator with the titration phase of the newer agent should prevent rebound activity and limit off-target effects, particularly cardiac events.

Natalizumab

Most often the reason for switching from natalizumab to an S1P modulator is to reduce the risk of carry-over PML from natalizumab. In our centre, we do an MRI and lumbar puncture for cerebrospinal fluid analysis to exclude JC virus DNA on PCR (polymerase chain reaction test). Provided these two tests are clear, we typically initiate S1P modulators within 4 weeks of the last natalizumab infusion. A prolonged wash-out period (8 weeks or longer) is associated with rebound disease activity on stopping natalizumab and is therefore not recommended. It is important that all the recommended baseline screening tests and vaccination reviews are done before starting an S1P modulator.

Teriflunomide

Because teriflunomide has such a long half-life, some neurologists would recommend an accelerated washout using cholestyramine or activated charcoal. Rheumatologists rarely do this when switching patients with rheumatoid arthritis from leflunomide (teriflunomide prodrug) to other DMTs, so I am not sure this accelerated washout is necessary. It is important that all the recommended baseline screening tests and vaccination reviews are done before starting an S1P modulator.

If the main reason for switching from teriflunomide is leukopaenia or lymphopaenia I would recommend waiting for the neutrophil and lymphocyte counts to go above 1,000/mm³ and 800/mm³ respectively. Similarly, if the switch is for abnormal LFTs on teriflunomide you would ideally want the liver enzymes to normalise or at least drop to below 3x the upper limit of normal.

Fumarates

It is important that all the recommended baseline screening tests and vaccination reviews are done before starting an S1P modulator. If the main reason for switching from a fumarate is lymphopaenia, I would recommend first waiting for the peripheral blood neutrophil and lymphocyte counts to go above 1,000/mm³ and 800/mm³, respectively.

Alemtuzumab

It is important that all the recommended baseline screening tests and vaccination reviews are done before starting an S1P modulator. I would recommend first waiting for the total peripheral blood neutrophil and lymphocyte counts to go above 1,000/mm³ and 800/mm³, respectively.

Anti-CD20 therapies (selective cell depleting DMTs)

It is important that all the recommended baseline screening tests and vaccination reviews are done before starting an S1P modulator.

Cladribine (selective cell depleting DMT)

Mitoxantrone

HSCT

It is important that all the recommended baseline screening tests and vaccination reviews are done before starting an S1P modulator. I would recommend first waiting for the peripheral blood neutrophil and lymphocyte counts to go above 1,000/mm³ and 800/mm³ respectively.

DMTsShort

S1P modulators – short summary

27/02/2023 Gavin Giovannoni

Summary

Trade names

Gilenya (fingolimod), Mayzent (siponimod), Zeposia (ozanimod), Ponvory (ponesimod).

Mode of action

Sphingosine 1-phosphate (S1P) receptor modulators block the capacity of lymphocytes to egress from lymph nodes, causing their redistribution, rather than depletion.

Efficacy

High.

Class

Maintenance, immunosuppressive.

Immunosuppression

Yes, systemic.

Dosing

Fingolimod dosing

Adults: one 0.5 mg capsule orally once daily.
Children (10 years and above): one 0.25 mg or 0.5 mg capsule orally once daily, dependent on body weight.

Siponimod dosing

Treatment is titrated upwards for days 1 ̶ 6 to reduce off-target side effects. Genotyping is carried out before starting treatment to determine dose, based on your speed of metabolising siponimod.

Slow metabolisers: should not take siponimod
Intermediate metabolisers: 1 mg per day
Rapid metabolisers: 2 mg per day.

Ozanimod dosing

0.92 mg once daily; treatment is titrated upwards for days 1 ̶ 7, to reduce off-target side effects.

Ponesimod dosing

20 mg once daily; treatment is titrated upwards for days 1 ̶ 14, to reduce off-target side effects.

Dose reduction

In cases of persistent lymphopaenia, the European Medicines Agency recommends stopping S1P modulator administration until lymphocyte counts recover.

Main adverse events and monitoring requirements

Transient slowing of the heart rate; raised liver enzymes.
Infection risk (opportunistic infections, lymphomas, fungal infections); skin cancer; progressive multifocal leukoencephalopathy.
Macular oedema; regular self-monitoring advised; routine clinic monitoring in at-risk patients.
Rebound disease activity: repeat MRI scan recommended 3 ̶ 6 months after treatment start.

Rare adverse events of special interest

Rare potential for heart block (associated with slowed heart rate) necessitates initial dose titration for all S1P modulators and cardiac monitoring with fingolimod.
Rare cases of posterior reversible encephalopathy syndrome; requires urgent medical attention.

Further details about S1P modulators

Switching-2-S1P modulators

Switching