With dysfunction of the posterior columns in the cervical region, neck flexion may elicit a sudden

“electric-like” sensation down the back or into the arms (Lhermitte’s sign or “barber’s chair syndrome).

APPROACH TO PERIPHERAL NEUROPATHY

Various nerve fibers and their functions are depicted in Figure 6E.11.

Fig. 6E.11: Various nerve fibers and their function.

Clinical Types of Neuropathy

Polyneuropathy: It is the most common variety of neuropathy. The nerve fibers are affected in a

length-dependent pattern; toes and soles are affected first and hands later. A majority of these cases

occur due to metabolic, toxic, or systemic disorders.

Causes of polyneuropathy

Diabetes mellitus

Alcohol

Nutritional (B12 deficiency)

Guillain-Barré syndrome

Toxins (Pb, As, Zn, and Hg)

Hematologic (paraproteins)

Endocrine (hypothyroid)

Rheumatologic (systemic lupus erythematosus, rheumatoid arthritis, and vasculitis)

Amyloid

Porphyria

Infectious (syphilis, human immunodeficiency syndrome)

Sarcoid

Tumor (paraneoplastic)

“DANG THERAPIST”

Mononeuropathy: Mononeuropathy refers to single peripheral nerve involvement and usually

occurs due to trauma, compression, or entrapment.

Causes of mononeuropathy

Acute: Sustained pressure, e.g. tourniquet

Chronic: Entrapment.

Causes (according to site of compression)

Carpal tunnel Median nerve

Cubital tunnel Ulnar nerve

Spiral groove of humerus Radial nerve

Inguinal ligament Lateral cutaneous of thigh (meralgia paresthetica)

Neck of fibula Common peroneal nerve

Flexor retinaculum (Tarsal tunnel) Posterior tibial nerve

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Entrapment neuropathies are commonly seen in

Endocrinal (diabetes mellitus, myxedema, acromegaly)

Amyloidosis

Hereditary neuropathy susceptible to pressure palsy

Pregnancy

Arthritis (rheumatoid)

Multiple mononeuropathies/mononeuritis multiplex refers to the involvement of multiple,

separate noncontiguous peripheral nerves either simultaneously or sequentially.

Causes of mononeuritis multiplex

Leprosy (most common)

Diabetes mellitus

Vasculitis

Sarcoidosis

Amyloidosis

Malignancy

Neurofibromatosis

HIV infection

Idiopathic multifocal motor neuropathy

PATHOLOGIC CLASSIFICATION OF NEUROPATHIC DISORDERS (FIGS.

6E.12A AND B)

1. Neuronopathies (pure sensory or pure motor):

Sensory neuronopathies (ganglionopathies)

Motor neuronopathies (motor neuron disease)

Sensory neuronopathy Motor neuronopathy

Ganglion cells predominantly affected

Both proximal and distal involvement

Sensory ataxia is common

No weakness

But awkward movement due to sensory

disturbances

Example:

Cancer (paraneoplastic)

Sjogren’s syndrome

Cisplatin and other analogs

Vitamin B6

toxicity

HIV–related sensory neuronopathy

Disorder of anterior horn cells. Weakness, fasciculation, atrophy not truly a process

of peripheral nerves

2. Peripheral neuropathies (usually sensorimotor):

Myelinopathies

Axonopathies

Axonal neuropathy Demyelinating neuropathy

Usually gradual and insidious onset Usually acute or subacute

Large and long axons are affected early, hence initially lower extremeties are

affected

Diffuse process, starts in lower limbs. But not

always distal

Stocking-glove sensory motor loss results in symmetrical distal clinical signs in

legs and arms

Generalized weakness and mild sensory loss

Distal involvement Proximal and distal involvement

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Ankle jerk lost early and proximal tendon reflexes preserved All reflexes are lost early

Muscle wasting common Relatively absent

Cerebrospinal fluid (CSF) proteins normal CSF proteins elevated (since nerve roots are

involved)

Slow recovery Rapid recovery

Residual deformity common Residual deformity less common

Nerve conduction normal or slightly lowered Nerve conduction is slowed

Figs. 6E.12A and B: Classification of neuropathy based on history and examination.

(DM: diabetes mellitus; HNPP: hereditary neuropathy with liability to pressure palsies; CIDP: chronic

inflammatory demyelinating polyneuropathy; MMN: multifocal motor neuropathy; GBS: Guillain–Barré

syndrome)

APPROACH TO POLYNEUROPATHY

What is the onset and temporal evolution?

Acute (days to 4 weeks)

Subacute (4–8 weeks)

Chronic (>8 weeks)

Acute onset Guillain-Barré syndrome

Acute intermittent porphyria

Critical illness polyneuropathy

Thallium toxicity

Subacute onset Toxins or medications

Nutritional deficiency

Metabolic abnormality

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Paraneoplastic syndrome

Chronic Hereditary motor and sensory neuropathy (HMSN)

CIDP

CKD

Relapsing/remitting course Guillain-Barré syndrome

CIDP

HIV/AIDS

Porphyria

(CIDP: chronic inflammatory demyelinating polyneuropathy; CKD: chronic kidney disease; HIV: human

immunodeficiency virus; AIDS: acquired immunodeficiency syndrome)

What systems are involved?

Motor (or) sensory (or) autonomic (or) mixed

Motor symptoms

Negative symptoms Positive symptoms

Weakness Wasting

Loss of dexterity

In the early stage, weakness in peripheral neuropathy is

distal; however, early proximal weakness is a feature of

demyelinating neuropathy and porphyric neuropathy

Cramps

Tremors

Fasciculations

Spasms

Neuropathic disorders that may have only motor symptoms at presentation

Motor neuron disease

Lead intoxication

Acute porphyria

Guillain-Barre Syndrome

Hereditary motor neuropathy

CIDP

Diphtheria

Brachial neuritis

Diabetic lumbosacral plexus neuropathy

Sensory symptoms

Negative symptoms Positive symptoms

Numbness, loss of sensation in hands and feet Burning, pain, walking on cotton wool, band-like sensation on feet or

trunk, stumbling, tingling, pins, and needles

Large fiber neuropathy—neuropathy of signs/ataxic

neuropathy

There are few symptoms (numbness, ataxia) but lots of

signs (loss of vibration, joint position sense, diminished

reflexes, Romberg’s sign positive)

Small fiber neuropathy—neuropathy of symptoms

Lots of symptoms (PAIN—burning, shock like, stabbing, prickling,

shooting, lancinating, allodynia, tight band like pressure. Insensitive

to heat and cold) but very few signs (loss of pain, temperature)

Examples:

Sjogren’s syndrome

Vitamin B12 neuropathy

Cisplatin

Pyridoxine neurotoxicity

Friedreich’s ataxia

Examples:

Diabetes

Amyloidosis

Fabry’s disease

HIV

Tangier’s disease

Hereditary sensory and autonomic neuropathy

Sjogren’s syndrome

Chronic idiopathic small fiber sensory neuropathy

Small and large fiber neuropathy—pan sensory: Global sensory loss

Example:

Carcinomatous sensory neuropathy

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