Neuromuscular diseases - Peripheral Neuropathys Flashcards
General outline of PNS pathway
Sensory input -> spinal cord -> Brain -> Spinal cord -> Motor output
the 2 motor divisions
Somatic (Skeletal muscle) and Autonomic (Smooth muscle, glands, cardiac)
What is a plexus?
Network of nerve cells extending from the root to the branches. 4 main ones in PNS (Brachial, Cervical, Lumbar and Sacral)
2 Classifications of Peripheral Neuropathy?
Axonal and Demyelinating
How would you find out whether a peripheral neuropathy is axonal or demyelinating?
Electrophysiological testing (nerve conduction data). Low amplitude of action potential indicates axonal neuropathy, low latency of action potential equals demyelinating neuropathy
What is the clinical adjunctive information used in diagnoses?
Upper or lower limb
Proximal or Distal
Symmetrical or Asymmetrical
Acute or Chronic
In how many cases of peripheral neuropathy is no cause found?
50%
Case1: 56. F
* Pain / numbness in medial border of right
hand at night
* Getting worse over 2 years
* Noticed recently the base of her thumb
was thinner
* Works as a secretary, has rheumatoid
arthritis and diabetes
Diagnoses?
Carpal Tunnel Syndrome - entrapment neuropathy of median nerve
Diagnoses is clinical with supporting nerve conduction tests show a slowing across the wrist - demyelinating
Treatment includes rest, splints
Asymmetrical Focal neuropathy of the facial nerve is known as what?
Bells Palsy syndrome - evolves over 72 hours
Treated with corticosteroids which leads to a 90% recovery rate
- F
Presents to her GP with a 5 year progressive change
in sensation in her feet
Initially painful, and now numb
Over the last year she has noticed that she is numb
to just below the knees
No symptoms in her hands
Past medical history
Diabetic with poor control
Previous chemotherapy for breast cancer
Ex-alcoholic (stopped drinking 3 years ago)
Examination
Strong normal power in ankle
Numb to pin prick and hot and cold to the knees
absent ankle-jerk reflex
low amplitudes, normal nerve velocities in nerve conduction studies
Chronic lower limb distal symmetrical axonal sensorimotor neuropathy or Chronic Axonal Polyneuropathy
Onset and progression of Chronic Axonal Neuropathy
Mid-late adulthood onset and slowly progresses (usually years) with sensory alteration beginning in feet and progressing proximally
Treatment of CAN
Foot care, tackling long term risk factors, supportive (information, advice, home adaptations)
Case 3
* 25. F
* Fit and well student
* Had diarrhea 3/52 ago (bad takeaway)
* Then over 5 days has noticed progressive
sensory loss and weakness in feet and
now hands
* Is struggling to walk across the room
* Has fallen over multiple times
* Also feels short of breath at rest
Weak respiratory muscles
Over next 3 days becomes weaker and admitted to ICU
Guillain-Barre Syndrome
(Acute Inflammatory Demyelinating Polyneuropathy)
What is GB Syndrome usually preceded by?
GI or upper respiratory tract infection 2/3rds of the time
Mechanism in which bacteria induce nerve demyelination?
Ganglioside Mimicry - infection inducing crossreactive antiganglioside antibodies which go on to bind to nodes of ranvier and form membrane attack complex and macrophage
Treatment of GB syndrome
Ensuring swallow and respiratory function are monitored
Plasma exchange or Intravenous IG can assist in speeding up recovery
Mortality is 4-7% with 60-80% of people walking again at 6 weeks
Case 4
* 47. M
* Presents with 3 month history of weakness and
sensory loss in both hands
* Progressed to involve both feet (L>R)
* Several falls, dropping objects
* Previously entirely fit and well
Significant weakness of both hands (asymmetric) and
biceps
* Very significant sensory loss in both hands and feet.
Unable to feel floor
* Moderately weak ankle strength
* Very weak hands
* Patchy preserved reflexes
* Nerve conduction studies show very slow motor and
sensory responses
Chronic Inflammatory demyelinating polyneuropathy (CIDP)
Progression and investigations for CIDP?
Progression generally happens over 8 weeks and in investigations you would see an acellular high protein CSF on lumbar puncture as you would with GB syndrome
Pathogenesis of CIDP
Activation of autoreactive T cells, release of inflammatory mediators and crossing of Blood nerve barrier, breakdown of BNB that allows autoreactive antibodies to cross.
Macrophage mediated demyelination, deposition of membrane attack complex
Antibodies binding at node of Ranvier could block nodular function or fixate complement to the node leading to destruction
Treatment of CIDP
Corticosteroid - 65-90% response rate
Slow speed but no relapses, can have long term complications. Also cheap
IVIg - 70% response rate
rapid response speed but can have relapses.
Costly treatment and can alter blood product
Plasma Exchange- 80% response rate
Rapid response rate, can have relapses.
Less costly than IVIg but invasive procedure
Case 6
* 14 year old girl presents with numb and weak
ankles that have developed over 2 years
* Poor at sport at school
* Mum has similar problems
* Noticed to have high arched feet (like mum)
Examination reveals a loss of muscle bulk in the
calves
* Reduced sensation feet to knees
* Absent reflexes in legs
* NCS – demyelinating sensorimotor neuropathy in
legs
Charcot-Marie-Tooth disease
Is CMT an axonal or demyelinating chronic neuropathy?
It can be either depending on the genes that carry the mutation
What is AMAN?
Acute Motor Axonal Neuropathy - is an axonal variant of Guillian-Barre syndrome. Similar in presentation to GB Syndrome but more severe and prolonged, with slower recovery.
