Multiple Sclerosis Flashcards
What is MS?
Multiple sclerosis (MS) is a chronic and progressive condition that involves demyelination of the myelinated neurones in the central nervous system. This is caused by an inflammatory process involving the activation of immune cells against the myelin.
MS typically presents in?
young adults (under 50 years) and is more common in women. Symptoms tend to improve in pregnancy and in the postpartum period.
Pathophysiology of MS
Myelin covers the axons of neurones in the central nervous system. This myelin helps the electrical impulse move faster along the axon. Myelin is provided by cells that wrap themselves around the axons. These are Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.
Multiple sclerosis typically only affects the central nervous system (the oligodendrocytes). There is inflammation around myelin and infiltration of immune cells that cause damage to the myelin. This affects the way electrical signals travel along the nerve leading to the symptoms of multiple sclerosis.
When a patient presents with symptoms of a clinical “attack” of MS, for example, an episode of optic neuritis, there are usually other lesions of demyelination at the same time throughout the central nervous system, most of which are not causing symptoms.
In early disease, re-myelination can occur and symptoms can resolve. In the later stages of the disease, re-myelination is incomplete and symptoms gradually become more permanent.
A characteristic feature of MS is that lesions vary in their location over time, meaning that different nerves are affected and symptoms change over time. The key expression to remember to describe the way MS lesions change location over time is that they are “disseminated in time and space”.
Causes of MS
The cause of the demyelination is unclear, but there is growing evidence that it is influenced by a combination of:
Multiple genes
Epstein–Barr virus (EBV)
Low vitamin D
Smoking
Obesity
Signs and Symptoms of MS?
Optic neuritis: eye movement abnormalities
Focal weakness
Focal sensory symptoms
Ataxia
eye movement abnormalities which could present in MS?
Patients may present with double vision due to lesions with the sixth cranial nerve (abducens nerve). There are two key phrases to remember to describe a sixth cranial nerve palsy: internuclear ophthalmoplegia and conjugate lateral gaze disorder.
Unilateral lesions in the sixth nerve causes a condition called internuclear ophthalmoplegia. Internuclear refers to the nerve fibres that connect between the cranial nerve nuclei that control eye movements (3rd, 4th and 6th cranial nerve nuclei). The internuclear nerve fibres are responsible for coordinating the eye movements to ensure the eyes move together. Ophthalmoplegia means a problem with the muscles around the eye.
Lesions in the sixth cranial nerve cause a conjugate lateral gaze disorder. Conjugate means connected. Lateral gaze is where both eyes move together to look laterally to the left or right. It is disordered in a sixth cranial nerve palsy. When looking laterally in the direction of the affected eye, the affected eye will not be able to abduct. For example, in a lesion affecting the left eye, when looking to the left, the right eye will adduct (move towards the nose) and the left eye will remain in the middle as the muscle responsible for making it move laterally is not functioning.
Focal weakness can present in MS:
Bells palsy
Horners syndrome
Limb paralysis
Incontinence
Focal sensory symptoms can present in MS:
Trigeminal neuralgia
Numbness
Paraesthesia (pins and needles)
Lhermitte’s sign is an electric shock sensation that travels down the spine and into the limbs when flexing the neck. It indicates disease in the cervical spinal cord in the dorsal column. It is caused by stretching the demyelinated dorsal column.
Ataxia can present in MS:
Ataxia is a problem with coordinated movement. It can be sensory or cerebellar:
Sensory ataxia is the result of loss of the proprioceptive sense, which is the ability to sense the position of the joint (e.g. is the joint flexed or extended). This results in a positive Romberg’s test and can cause pseudoathetosis.
Cerebellar ataxia is the result of problems with the cerebellum coordinating movement. This suggestions cerebellar lesions.
Disease Patterns in MS?
Clinically Isolated Syndrome
Relapsing-Remitting
Secondary Progressive
Primary Progressive
Clinically Isolated Syndrome
This describes the first episode of demyelination and neurological signs and symptoms. MS cannot be diagnosed on one episode as the lesions have not been “disseminated in time and space”. Patients with clinically isolated syndrome may never have another episode or develop MS. If lesions are seen on MRI scan then they are more likely to progress to MS.
Relapsing-Remitting
Relapsing-remitting MS is the most common pattern at initial diagnosis. It is characterised by episodes of disease and neurological symptoms followed by recovery. In MS the symptoms occur in different areas with different episodes. This can be further classified based on whether the disease is active and/or worsening:
Active: new symptoms are developing or new lesions are appearing on MRI
Not active: no new symptoms or MRI lesions are developing
Worsening: there is an overall worsening of disability over time
Not worsening: there is no worsening of disability over time
Secondary Progressive
Secondary progressive MS is where there was relapsing-remitting disease at first, but now there is a progressive worsening of symptoms with incomplete remissions. Symptoms become more and more permanent. Secondary progressive MS can be further classified based on whether the disease is active and/or progressing.
Active: new symptoms are developing or new lesions are appearing on MRI
Not active: no new symptoms or MRI lesions are developing
Progressing: there is an overall worsening of disease over time (regardless of relapses)
Not progressing: there is no worsening of disease over time
Primary Progressive
Primary progressive MS is where there is a worsening of disease and neurological symptoms from the point of diagnosis without initial relapses and remissions. This can be further classified in a similar way to secondary progressive based on whether it is active and/or progressing.
Diagnosis of MR
Diagnosis is made by a neurologist based on the clinical picture and symptoms suggesting lesions that change location over time. Symptoms have to be progressive over a period of 1 year to diagnose primary progressive MS. Other causes for the symptoms need to be excluded.
Investigations can support the diagnosis:
MRI scans can demonstrate typical lesions
Lumbar puncture can detect “oligoclonal bands” in the cerebrospinal fluid (CSF)
