Neuro - MS Flashcards
What is a relative afferent pupillary defect (RAPD)?
RAPD = sign of optic neuropathy (CN II)
Sign of pathology in; optic nerve (proximal to chiasm), retina or eye itself
Detected via ‘swinging light test’ - shine light into one of the pt’s eyes, then the other and then back to the first eye
- Normal = pupil remains constricted (equal direct and consensual constriction)
- RAPD = pupil appears to dilate when light is move from unaffected eye to the affected one (direct light response < consensual light response)
Optic Neuritis:
- What is it?
- What causes it?
- Features of ON?
- Management?
Optic neuritis = demyelinating inflammation of the optic nerve (CN II)
Causes:
- Multiple sclerosis (ON is often the 1st symptom)
- Diabetes
- Syphilis
Features:
- unilateral ↓ in visual acuity (over hours-days)
- poor discrimination of colours ‘red desaturation’ - red colour appears ‘washed out’ in affected eye
- eye pain - worse on movement
- RAPD
- central scotoma - partial visual loss / blind spot
- Pale optic disc on fundoscopy (papillitis = inflammation of optic nerve head)
Management:
- Steroids e.g. Methyl Prednisolone 1g oral / IV once daily for 3 days (morning)
- If partial response, extend course to 5 days
- Recovery = 4-6 weeks
What investigations might you do in a pt with optic neuritis?
Tests looking for evidence of systemic inflammation (in which ON is a feature):
CRP, ESR - inflammation markers
Serology for autoimmune conditions:
- ANA, ANCA, ds-DNA, ENA, anticardiolipin antibodies, serum ACE
- +ve result on the above could indicate; GPA, EGPA, antiphospholipid syndrome, sarcoidosis etc.
Serology for infectious triggers (rare cause of ON):
- HIV, syphilis, hepatitis B and C
Antibodies for neuromyelitis optica (Devic’s disease):
- anti-AQP4 (auto-antibodies against aquaporin 4)
- anti-MOG (auto-antibodies against myelin oligodendrocyte glycoprotein)
- anti-NF (auto-antibodies against neurofascins)
In which areas of the nervous system could a pathology cause unsteadiness of gait i.e. gait ataxia?
Cerebellum + cerebellar connections to brain - CEREBELLAR ATAXIA
- Stacatto dysarthria (DANISH)
- Sudden, ipsilateral arm + leg weakness = stroke
Dorsal columns of the spinal cord - SENSORY ATAXIA
- L’Hermitte’s sign - tingling/electrical sensation in back + limbs when flexing or extending head (spinal cord specific)
- Tight band-like sensation around torso
- Urinary urgency + frequency (rarely seen in peripheral nerve pathology)
- Other symptoms as in peripheral nerves below …
Peripheral nerves / nerve roots (large myelinated fibres) - SENSORY ATAXIA
- Altered sensation e.g. parasthesia, numbness
- Balance worse in the dark/when eyes shut (due to loss of vision to balance self + proprioceptive impairment)
Vestibular apparatus + connections
- Vertigo (worse on head movement)
- Nausea / vomiting
- Sometimes hearing loss and/or tinnitus
What are some of the risks of steroids acutely?
- GI disturbance - give PPI
- Agitation / restlessness
- Insomnia
- Steroid psychosis - behavioural change
- Weight gain
- Avascular necrosis of femoral head (rare)
What tests need to be done prior to a course of steroids?
Check for signs of systemic infection!!
(steroids = immunosuppresive)
- FBC
- U+Es
- eGFR - assess renal function
- Blood glucose
- CRP / ESR
- Urine dipstick - UTI
What blood test is important in a pt with a high signal lesion of the posterior cervical cord on MRI?
Serum B12
Vitamin B12 deficiency can produce ↑ T2-weighted signal (white lesion) or ↓ T1-weighted signal of the posterior or lateral spinal cord - mainly cervical or upper thoracic segments
What is a MRI brain scan with injection of Gadolinium contrast used for?
Gadolinium contrast = highlights areas of BBB breakdown - which suggests active / recent inflammation
Sometimes done in the context of multiple sclerosis to differentiate old vs new white-matter lesions
- Old lesions - inactive inflammation
- New lesions - active/recent inflammation
Evidence of new + old lesions = typical of relapsing-remitting MS ‘lesions disseminated in time and place’
T2 weighted image - will show BOTH old + new white-matter lesions (white lesion contrasted against grey coloured white-matter) - left image
T1 weighted image + Gadolinium contrast - shows ‘new’ white-matter lesions (as white lesion against grey coloured background) - right image
What do lesions typical of multiple sclerosis look like on T2 MRI?
They appear as small high signal lesions (white in contrast to background)
Lesions can be in many locations, but one common one is periventricular white matter
How are acute, MS relapses managed?
1st line = High-dose steroids e.g. Methyl Prednisolone
- In patient –> IV Methyl Prednisolone 1g OM, for 3 days (morning)
- Out-patient –> Oral Methyl Prednisolone 500mg OM, for 5 days (just as effective as in-patient IV)
Notes:
- Steroids ↓ length of acute relapse but do not alter degree of recovery
- Beneficial effects of successive steroid courses tend to diminish
- Check for presence of infections BEFORE prescribing
- If patient is diabetic then close serum glucose monitoring
What are the criteria for a MS patient to receive ‘disease-modifying treatment’?
Patient must have 2 or more significant relapses over a 2 year period
Describe the common course of multiple sclerosis?
Often it presents as relapsing-remitting (RR-MS) i.e. several episodes of symptoms with recovery in between and good seperation between episodes.
It can then develop into Secondary Progressive MS (SPMS) and become a steady decline in function over time.
What does the drug Baclofen do?
Used to manage muscle spasticity
(such as that caused by spinal cord injury or MS)
Uses:
- ↓ muscle spasticity
- hiccups / muscle spasms near end of life
MoA: derivative of GABA –> acts on GABAB receptors in spinal cord and brainstem
Side effects:
- Sedation - dose required for spasticity management causes this
- Dizziness
- Insomnia
- Nausea / vomiting
- Urinary retention / constipation
- If stopped suddenly –> seizures / rhabdomyolysis
How is neuropathic pain described?
What symptoms can appear alongside it?
How is it managed in MS?
Neuropathic Pain - MS
Neuropathic pain = burning or stabbing
Common accompanying symptoms:
- paradoxical numbness
- paraesthesia
- hyperpathia (an increased sensitivity to painful stimuli)
- allodynia (when a non-painful stimulus is perceived as painful)
e. g. pain induced by bedclothes touching the feet
Gabapentin can be used for neuropathic pain in MS
- Is an AED (voltage-gated Ca2+ channels)
How does oxybutynin work?
Oxybutynin:
Uses:
- Urinary frequency / urgency / incontinence
MoA:
- Inhibits muscarinic ACh receptors
- This inhibits parasympathetic stimulation of bladder detrusor muscle
- Results in ↓ urgency and frequency
Side effects (anti-cholinergic):
- Dry mouth
- Constipation
- Drowsiness
- Dizziness
- Difficulty urinating
