PERIPHERAL NEUROPATHYNeuropathy: a pathological process affecting a peripheral nerve or nerves.

DEFINITIONS

Mononeuropathy: process affecting a single nerve.

Mononeuritis multiplex: affecting several or multiple nerves.

Polyneuropathy: a diffuse, symmetrical disease usually beginning peripherally. Demyelinating: with damage to schwann cells,

slows conduction. E.g. GBS. Axonal degeneration: primarily damages axons,

some die back from the peripheries. Conduction velocity remains.

HOW DO THE SX A NEUROPATHY CLASSICALLY DIFFER FROM A MYOPATHY?

Myopathy: A disease of voluntary muscles usually Weakness is the predominant feature Proximal muscle wasting common Decrease Tone and Power Normal sensory and reflex function.

AETIOLOGIES OF PERIPHERAL NEUROPATHY

Genetic: Charcot-Marie-Tooth disease most common Prev: 4 in 100 000. Clinical phenotype:

Progressive distal wasting of limbs, especially the foot.

Mild distal sensory loss. Absent/reduced reflexes in lower limb. High arched foot. Intrinsic hand muscles affected.

Charcot Marie Tooth disease

DRUGS/TOXINS

Heavy metals: arsenic, lead, mercury, thallium

Drugs: isoniazid, ethambutol, phenytoin, lithiumcarbonate, disulfiram, metronidazole.

NB: a generalized peripheral neuropathy may sometimes follow an allergic response/immune response to vacccinations and injections of foreign proteins.

METABOLIC/ENDOCRINE - DIABETES

Neuropathy predom sensory and symmetrical Thought to be due to overloading glucose

pathway, resulting in inc levels of sorbitol and fructose, leading to damage.

Diabetic patients may get diabetic amyotrophy: P/C: painful wasting, usually symmetrical of

quadriceps muscles. Knee reflexes diminished. Associated with poor glycaemic control.

VITAMIN DEFICIENCIES.

Vit12 def: mostly a sensory neuropathy that maybe accompanied by degeneration of spinal chord.

Vit B1 (thiamine def): a/w chronic alcoholism and severe nutritional disturbances, painful, mostly sensory neuropathy.

Alchoholism: Sx: pain in calves, burning feet, distal weakness. Signs: distal muscle wasting, absent knee and

ankle jerks, distal sensory impairment, tender calves.

Caused by vit B def rather than direct affects of alcohol.

INFLAMMATORY: GBS

Guillian Barre syndrome (an acute inflammatory demyelinating polyneuropathy): circulating anti-myelin antibodies.

Most common polyneuropathy: 3 per 100 000 per year.

Monophasic (does not recur), usually demyelinating. Humoral and cell-mediated response against myelin

in peripheral nerves and spinal roots. Paralysis follows 1-3 weeks after infection (most

causes unknown but CMV and campylobacter jejuni are 2 well recognised causes)

Ascending distal muscle weakness that progresses over several days to 6 weeks.

INFLAMMATORY: GBS

Ix: Increased CSF protein and no WBC or raised glucose.

Ix: Nerve conduction study to diagnose it (demyelinating).

Rx: supportive therapy. High dose immunoglobulins within first 2 weeks reduced duration and severity.

OTHER

Malignancies: paraneoplastic manifestations, ?chemo.

Connective tissue disorders: RA, SLE, sarcoid. Nerve entrapment: carpal tunnel, etc. Infections:

Leprosy – most common worldwide cause of peripheral neuropathy. Mycobacterium leprae invades schwann cell

HIV/AIDS: by the virus itself or drug treatment

ELECTROMYOGRAPHY (EMG)

TO DISTINGUISH NEUROPATHY VS MYOPATHY. A needle electrode is inserted into muscle,

electrical activity detected and tested. Useful as weakness and impaired muscle

strength can be due to: Problems in muscle, in the nerves, the spinal

chord, are of brain that controls the muscle. “EMG’s help differentiate primary muscle

conditions from muscle weakness caused by neurological disorders”

NERVE CONDUCTION STUDIES

Used to evaluate the function, esp electrical conduction, of sensory and motor nerves in PNS.

Usually done in conjunction with EMG. Measures:

Nerve conduction velocity Time taken for transmission and reception of

signals Sensory AP’s Muscle AP’s

Help diagnose: carpal tunnel, ulnar neuropathy, GBS, etc.

NEUROPATHIC PAIN

Difficult to treat and often responds poorly to standard pain treatments.

Three major classes used:1. Tricyclic antidepressants2. Anti-convulstants3. Opiates

TRICYCLIC ANTIDEPRESSANTS

Block neuronal reuptake of serotonin and NA via inhibiting membrane pumps.

Most commonly used: amitriptyline. SE: hypotension (avoid in heart block)

NB: newer antidepressants such as SSRI inconsistent with analgaesiac properties and not recommended for analgaesia.

Used in diabetic neuropathy.

ANTI-CONVULSANTS

Gabapentin: newest anti-convulsant Widespread usage in neuropathic pain, but exact

site and mechanism of action unknown. Remarkably well tolerated with few interactions. Expensive.

Carbamazepine: old anti-convulsant Na channel blocker. SE: dizziness, headache, allergic rashes,

oedema, etc

OPIATES

Oxycodone Binds to U-receptors. Problems with efficacy and addiction.

DIABETIC NEUROPATHY

Variety of syndromes which affect sensory, autonomic and motor fx.

Widely held definition: "the presence of symptoms and/or signs of peripheral nerve dysfunction in people with diabetes after exclusion of other causes."

DIABETIC NEUROPATHY

Commonest form: distal symmetrical sensory polyneuropathy. Distal sensory loss: numbness, tingling, loss of

ankle reflex and proprioception Often beginning in feet and spread prox. Hyperasthsia and dysaesthesia may occur. Neuropathic pain may develop: present at rest

and worse at night

DIABETIC NEUROPATHY

Autonomic neuropathy Cardiovascular: resting tachycardia, orthostatic

hypotension, silent angina or infarct. Gastroparesis Bladder fx abnormalities: incontinence.

PATHOLOGY

Most likely multifactorial and complex. Thought to be due to hyperglycaemia

Distal axonal loss with focal demyelination Resultant slowing of nerve conduction or loss

of it completely.

MX

Improved glycaemic control – greatest likelihood of preventing or slowing down the development of diabetic neuropaty

Treat hypertension and hyperlipidaemia Avoid neurotoxins eg smoking and ETOH Foot care: check daily, correct foot wear.

QUIZZ TIME

Muscle wasting is usually an early sign in myopathies (T/F)

Muscle weakness is a feature of both myopaties and neuropathies (T/F)

Name two drugs that can cause neuropathy. What dietary deficiencies can lead to

neurpathies?

QIZZ

What disease does this picture show? What category is it under?

QUIZZ

Name a form of mononeuropathy. A well known virus that can cause Guillina

Barre syndrome is the HSV. (T/F) GBS is predominantly an ascending sensory

neuropathy (T/F)

Choose the best answer A. ESR B. Nerve conduction Studies C. Electromyography D. CSF: high protein, normal WBC, high

glucose E: CSF: low protein, high WBC, normal

glucose G: CDF: high protein, normal WBC, n glucose H: he really liked her I: he really, really liked her J: contrary to what she said, it was ‘him’ and

not ‘her’A patient comes in with muscle weakness, and is a vague historian. You want to determine if it is a neuropathy, or a muscular disease.

Choose the best answer A. ESR B. Nerve conduction Studies C. Electromyography D. CSF: high protein, normal WBC, high

glucose E: CSF: low protein, high WBC, normal

glucose G: CDF: high protein, normal WBC, n glucose H: he really liked her I: he really really liked her J: contrary to what she said, it was ‘him’ and

not ‘her’A patient presents with weakness in his calf, that seems to be progressively affecting his quadriceps. You want to diagnose it.

Choose the best answer A. ESR B. Nerve conduction Studies C. Electromyography D. CSF: high protein, normal WBC, high

glucose E: CSF: low protein, high WBC, normal

glucose G: CDF: high protein, normal WBC, n glucose H: he really liked her I: he really really liked her J: contrary to what she said, it was ‘him’ and

not ‘her’What changes would you see on LP in a pt with GBS?

Choose the best answer A. ESR B. Nerve conduction Studies C. Electromyography D. CSF: high protein, normal WBC, high glucose E: CSF: low protein, high WBC, normal glucose G: CDF: high protein, normal WBC, n glucose H: he really liked her I: he really really liked her J: contrary to what she said, it was ‘him’ and not

‘her’ K. FBE

An elderly lady presents with a headache that gets worse when she brushes her hair.

Choose the best answer A. ESR B. Nerve conduction Studies C. Electromyography D. CSF: high protein, normal WBC, high glucose E: CSF: low protein, high WBC, normal glucose G: CDF: high protein, normal WBC, n glucose H: he really liked her I: he really really liked her J: contrary to what she said, it was ‘him’ and not

‘her’ K. FBE

A known alcoholic comes in to clinic complaining of sensory changes in his feet

Choose the best answer A. ESR B. Nerve conduction Studies C. Electromyography D. CSF: high protein, normal WBC, high

glucose E: CSF: low protein, high WBC, normal glucose G: CDF: high protein, normal WBC, n glucose H: he really liked her I: he really really liked her J: contrary to what she said, it was ‘him’ and

not ‘her’

Why was PHO so devo after being dumped by his ex?

REFERENCES

MedNoteShare, D Cheng, J Koh. Other