Neuromuscular diseases - Peripheral Neuropathys

Question 1

General outline of PNS pathway

Answer 1

Sensory input -> spinal cord -> Brain -> Spinal cord -> Motor output

Question 2

the 2 motor divisions

Answer 2

Somatic (Skeletal muscle) and Autonomic (Smooth muscle, glands, cardiac)

Question 3

What is a plexus?

Answer 3

Network of nerve cells extending from the root to the branches. 4 main ones in PNS (Brachial, Cervical, Lumbar and Sacral)

Question 4

2 Classifications of Peripheral Neuropathy?

Answer 4

Axonal and Demyelinating

Question 5

How would you find out whether a peripheral neuropathy is axonal or demyelinating?

Answer 5

Electrophysiological testing (nerve conduction data). Low amplitude of action potential indicates axonal neuropathy, low latency of action potential equals demyelinating neuropathy

Question 6

What is the clinical adjunctive information used in diagnoses?

Answer 6

Upper or lower limb
Proximal or Distal
Symmetrical or Asymmetrical
Acute or Chronic

Question 7

In how many cases of peripheral neuropathy is no cause found?

Answer 7

50%

Question 8

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?

Answer 8

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

Question 9

Asymmetrical Focal neuropathy of the facial nerve is known as what?

Answer 9

Bells Palsy syndrome - evolves over 72 hours
Treated with corticosteroids which leads to a 90% recovery rate

Question 10

65. 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

Answer 10

Chronic lower limb distal symmetrical axonal sensorimotor neuropathy or Chronic Axonal Polyneuropathy

Question 11

Onset and progression of Chronic Axonal Neuropathy

Answer 11

Mid-late adulthood onset and slowly progresses (usually years) with sensory alteration beginning in feet and progressing proximally

Question 12

Treatment of CAN

Answer 12

Foot care, tackling long term risk factors, supportive (information, advice, home adaptations)

Question 13

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

Answer 13

Guillain-Barre Syndrome
(Acute Inflammatory Demyelinating Polyneuropathy)

Question 14

What is GB Syndrome usually preceded by?

Answer 14

GI or upper respiratory tract infection 2/3rds of the time

Question 15

Mechanism in which bacteria induce nerve demyelination?

Answer 15

Ganglioside Mimicry - infection inducing crossreactive antiganglioside antibodies which go on to bind to nodes of ranvier and form membrane attack complex and macrophage

Question 16

Treatment of GB syndrome

Answer 16

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

Question 17

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

Answer 17

Chronic Inflammatory demyelinating polyneuropathy (CIDP)

Question 18

Progression and investigations for CIDP?

Answer 18

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

Question 19

Pathogenesis of CIDP

Answer 19

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

Question 20

Treatment of CIDP

Answer 20

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

Question 20

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

Answer 20

Charcot-Marie-Tooth disease

Question 21

Is CMT an axonal or demyelinating chronic neuropathy?

Answer 21

It can be either depending on the genes that carry the mutation

Question 21

What is AMAN?

Answer 21

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.