Neurology: Disorders Of The Peripheral Nerve Flashcards
What groups of peripheral neuropathies are there?
Hereditary motor sensory neuropathies
Acute post infectious polyneuropathy
Bell’s palsy and facial nerve palsies
What is an example of an inherited motor sensory neuropathy?
Charcot-Marie-Tooth disease
There are many forms of CMT disease, but they typically lead to…
Symmetrical, slowly progressive distal muscle wasting
Muscles below the knees usually affected and hands
In CMT disease, what sensory component is there?
Numbness in hands and feet
In CMT disease, what genes are there mutations in?
Myelin genes
CMT1A inherited in autosomal dominant manner in 2/3
1/3 develop the mutation de novo
How can children present with CMT disease?
May present in preschool with tripping from bilateral foot drop
Examination: loss of ankle reflexes progressing to loss of knee reflexes
Pes cavus
In CMT disease, are the lower limbs typically affected more?
Yes
Perineal muscles particularly effected
How is CMT disease diagnosed?
Nerve conduction studies - show motor and sensory neuropathy
Genetic testing
Nerve biopsy - onion bulb formation due to hypertrophic nerves
Why may affected nerves in CMT disease be hypertrophic ?
Due to demyelination followed by attempts at remyelination
Do those affected with CMT disease lose the ability to walk?
Rarely
What is an example of an acute post infectious polyneuropathy?
Guillian-Barre syndrome
Can GBS occur at any age?
Yes
When does GBS typically present?
2-3 weeks after an URTI or campylobacter gastroenteritis
How does GBS present?
Ascending, progressive, symmetrical weakness over a few days to 2 weeks
Loss of tendon reflexes
Autonomic involvement
Sensory symptoms occur, but less striking than motor weakness
Bilateral facial weakness
Involvement of bulbar muscles - difficulty chewing and swallowing
What autonomic features can occur with GBS?
Tachycardia/bradycardia HTN/orthostatic hypotension Urinary retention Ileus Loss of sweating
In GBS, are the proximal or distal muscles more affected?
Proximal - trunk, respiratory, cranial nerves
What muscle involvement required ITU transfer?
Respiratory- may require artificial ventilation
Start before established respiratory failure
Full recovery in cases of GBS occur in what percentage?
90% but can take up to 2 years
What investigations should be requested in suspected GBS?
MRI brain and spinal cord to identify/exclude spinal cord lesion - bleed, tumour, inflammatory transverse myelitis
CSF - protein markedly raised in GBS
Nerve conduction studies - reduced velocities
How is GBS managed?
Supportive - especially respiration
Corticosteroids no role, may delay recovery
IV immunoglobulin or plasma exchange
What is Bell palsy?
An isolated low motor neurone paresis of CN VII
What does Bell palsy lead to?
Ipsilateral facial weakness
