Polyneuropathies

Question 1

classification of polyneuropathies?

Answer 1

pathology: axonal degeneration or demyelinating disease

time course and pattern: acute symmetrical, chronic symmetrical or multiple mononeuropathy

Question 2

what is GBS (guillain-barre syndrome)?

Answer 2

acute ascending progressive neuropathy, 4 subtypes of which most common=
acute inflammatory demyelinating polyradiculopathy (95% of cases)

Question 3

preceeding features to neurological symptoms of GBS?

Answer 3

those of an infection, commonly GIT e.g. campylobacter jejuni, or RT e.g. mycoplasma
other implicated organsims include HIV, EBV and CMV

Question 4

what is Miller Fisher syndrome?

Answer 4

an overlap syndrome with GBS
inflammatory neuropathy affecting the cranial nerves, causing ophthalmoplegia, and accompanied by areflexia and ataxia but NOT weakness.

Question 5

who does GBS affect?

Answer 5

males more commonly

bimodal presentation: 15-35yrs, and 50-75yrs are the 2 peaks

Question 6

RFs for GBS?

Answer 6

infection-GI or resp 1-3wks prior to onsent of weakness
vaccinations
malignancy-hodgkin’s lymphoma
pregnancy-risk increases in the months after delivery

Question 7

where in the NS does GBS start?

Answer 7

in the nerve roots

Question 8

presentation of GBS?

Answer 8

weakness-starting 1-3wks post infection, acute symmetrical ascending starting in lower extremities, may be facial weakness, dysarthria or dysphasia, in severe cases can be resp failure
neuropathic pain e.g. backache and leg pain due to nerve root involvement
reflexes-may be reduced or absent
paraesthesia and sensory loss
ANS features-reduced sweating, reduced heat tolerance, paralytic ileus, urinary hesitancy.

Question 9

features of GBS o/e of pt?

Answer 9

hypotonia and reduced muscle power
facial weakness
hypo/areflexia
altered sensation or numbness
AN dysfunction-HR fluctuations, arrhythmias, labile BP, variable temp
resp muscle paralysis

Question 10

LP results in GBS?

Answer 10

raised protein with no elevation in cell counts

note rise in protein may not be seen until 1-2wks post onset of weakness

Question 11

most useful confirmatory test of GBS?

Answer 11

nerve conduction studies, should be repeated after 2 weeks if initially normal
initially may show F waves-delay in conduction due to nerve roots

Question 12

how is diagnosis of GBS made?

Answer 12

based on clinical hx and exam.
investigations:
EMG and nerve conduction studies
LP-high protein in CSF
Abs in blood to peripheral and central nerves
anti-ganglioside and campylobacter serology
stool culture, throat swab

Question 13

requirement of cardiac monitor in GBS patients?

Answer 13

need to monitor for ANS dysfunction:
cardiac arrhythmias
postural hypotension
HTN

Question 14

why might bloods in GBS show hyponatraemia?

Answer 14

SIADH can be assoc. with the condition- this would be a euvolaemic hyponatraemia with high urine osmolality

Question 15

most serious complication of GBS?

Answer 15

reps failure: occurs in 25%
need regular FVC monitoring with spirometry-QDS, if falling rapidly or FVC less than 1L then inform ITU as may need ventilation

Question 16

management of GBS?

Answer 16

note not all patients require treatment as disease is self-limiting
general measures: close monitoring as weakness is progressive
bedside spirometry-FVC 4 hourly, ventilatory support
ECG, cardiac monitoring
nutritional support
DVT prophylaxis
analgesia
laxatives
may need urinary catheter

specific:
Iv Ig
plasmapheresis-used within 1st 2 weeks of onset

Question 17

GBS complications?

Answer 17

acute resp failure
aspiration pneumonia
VTE
SIADH
renal failure caused by IV Ig
hypercalcaemia due to immobility
PAIN
ileus
persistent paralysis

Question 18

causes of painful peripheral neuropathy?

Answer 18

alcoholic neuropathy-alcohol destroys nerves and reduced absorption of B vitamins
diabetic amyotrophy*
porphyria
vti B1 or B12 deficiency-subacute combined degeneration of the SC
carcinoma

Question 19

causes of chronic polyneuropathy?

Answer 19

diabetic neuropathy
nutritional including alcohol (with or without vit B1 (thiamine) deficiency-dry beri beri (PN) and wet beri beri (HF)) and vit B12 deficiency
vascular-chronic vascular disease e.g. polyarteritis nodosa, SLE
infection-HIV, leprosy, diphtheria post infective-GBS, inflammtory-sarcoidosis, chronic inflammatory demyelinating polyneuropathy (CIDP)
metabolic-hypothyroidism, liver failure, CKD
malignancy-lung Ca, breast Ca, myeloma
idiosyncratic-drugs-isoniazid, phenytoin, gold
congenital-charcot marie tooth, friedrich’s ataxia

Question 20

most common cause of peripheral neuropathy?

Answer 20

DM

Question 21

types of neuropathy caused by diabetes mellitus?

Answer 21

• peripheral sensorimotor (chronic peripheral neuropathy)-sensory affected more than motor, glove and stocking distribution, loss of ankle reflexes and later knee, hands only affected in long standing neuropathy.
• acute diffuse painful (acute peripheral neuritis)-abrupt onset, burning foot pain espec. at night, unrelated to DM duration, assoc. with poor glycaemic control although may follow period of good control
• acute painful neuropathy of rapid improvement of blood glucose control-self-limiting
• diabetic amyotrophy (proximal motor)
• autonomic-cardiac, GI-gastroparesis, diarrhoea, GU-urinary hesitancy, overflow incontinence, gustatory sweating, anhidrosis
• mononeuorpathy-cranial nerves, CTS-surgery-longitudinal scar

Question 22

what is diabetic amyotrophy?

Answer 22

main motor manifestation
form of diabetic neuropathy in which pt complains of severe pain and paraesthesia in upper legs, with weakness and muscle wasting of thigh and pelvic girdle muscles
may be asymmetrical
may be extensor plantars
us. associated with period of very poor glycaemic control, sometimes with dramatic weight loss

once good glycaemic contol achieved, pain and weakness gradually reduce

Question 23

overall management considerations in diabetic neuropathy?

Answer 23

tight glycaemic control
regular surveillence for signs of neuropathy to allow early intervention
prevention of foot trauma

Question 24

GBS prognosis?

Answer 24

70% complete recovery at 1 year