what is MS
chronic, progressive autoimmune condition that causes demyelination in the CNS
occurs in 20-40s, f>m
pathophys of MS
- myelin covers axons of neurones to allow faster conduction. this myelin is provided by oligodendrocytes wrapping themselves around the axons in the CNS (in PNS its schwann cells)
- Inflammation and immune cell infiltration cause damage to the myelin, affecting the electrical signals moving along the neurones.
lesions vary in location, meaning that the affected sites and symptoms change over time.`(relapse-remit nature for most pts)
features of MS
- lethargy
- optic neuritis
- optic atrophy
- uhthoff’s phenomenon
- internuclear ophthalmoplegia
sensory:
pins/needles
numbness
trigeminal neuralgia
Lhermitte’s syndrome: paraesthesiae in limbs on neck flexion
motor:
spastic weakness in legs
cerebellar:
- ataxia
- tremor
others:
urinary incontinence
sexual dysfunction
intellectual deterioration
features of optic neuritis
Central scotoma (an enlarged central blind spot)
Pain with eye movement
Impaired colour vision
Relative afferent pupillary defect
treated with high dose oral steroids
whats the relative afferent pupillary defect
In optic neuritis, the afferent pathway (optic nerve/sensory) is damaged. When light is shone in the affected eye, the direct pupillary reflex is reduced because less signal reaches the brain. However, when light is shone in the unaffected eye, the affected eye still constricts normally via the consensual reflex, because its efferent (motor) pathway is intact. (edinger westphal nucleus) This difference produces a relative afferent pupillary defect (RAPD) on the swinging flashlight test.
what is uhthoff’s phenomenon
worsening of vision following rise in body temperature as heat further slows conduction
whats internuclear ophthalmoplegia
impaired horizontal eye movement due to a lesion in the medial longitudinal fasciculus (MLF).
The MLF is a nerve tract that connects the abducens nucleus (lateral rectus) of one side to the contralateral oculomotor nucleus (medial rectus) of the other side.
This coordination allows both eyes to move together horizontally.
Weak/absent adduction of the eye on the side of the lesion when looking toward the opposite side
Abducting eye (other eye) shows nystagmus
MLF lesion → ipsilateral eye cannot adduct, contralateral eye abducts with nystagmus → horizontal diplopia.
what is lhermitte’s sign
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.
investigations for MS
requires demonstration of lesions disseminated in time and space
MRI
high signal T2 lesions
periventricular plaques
Dawson fingers: often seen on FLAIR images - hyperintense lesions penpendicular to the corpus callosum
CSF - oligoclonal bands + increased intrathecal synthesis of IgG
management of MS
- acute relapse - oral or IV methylprednisolone for 5 days
- disease modifying therapies (mostly immunotherapies
- natalizumab (reduce risk of relapse)
for fatigue – amantadine
- spasticity - baclofen and gabapentin + physio
bladder –> anticholinergics or self catheter
depression – SSRI
oscillopsia - gabapentin
