Neuropathy and its classification

Shehzad Hussain

Nerve:

• A nerve is an enclosed, cable-like bundle of axons (the long, slender projections of neurons) in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs.

Peripheral nerve:

Cont…

• Each nerve is a cordlike structure that contains many axons, also called nerve fibres. Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called the epineurium.

Peripheral Neuropathy

• DEFINITION: It is inflammation and degeneration of the

peripheral nerves and/or the cranial nerves resulting in impairment of the conductivity of these nerves.

Common causes include systemic diseases (such as diabetes or leprosy), vitamin deficiency, medication (e.g., chemotherapy), traumatic injury, excessive alcohol consumption, immune system disease, or infection, or it may be inherited (present from birth)

Classification of Neuropathy

• Three main types of nerve can be involved in peripheral neuropathy:

• Autonomic nerves (not under conscious control, "automatic" or "involuntary" nerves)

• Motor nerves • Sensory nerves.

Cont…

• Peripheral neuropathy may be classified according to the number and distribution of nerves affected (mononeuropathy, mononeuritis multiplex or polyneuropathy), the type of nerve cell predominantly affected (motor, sensory, autonomic), or the process affecting the nerves; e.g., inflammation (neuritis), compression (compression neuropathy), chemotherapy (chemotherapy-induced peripheral neuropathy).

Causes:• Genetic diseases• Metabolic/endocrine• Toxic causes• Inflammatory diseases• Vitamin deficiency • Physical trauma• Chemotherapy • Others: electric shock, HIV, malignant disease,

radiation, shingles (Herpes zoster a viral infection)

Types of nerve fibersDiameter Conduction Function microns Velocity m/sA alpha 1-20 70-110 Motor, Proprioception

beta 5-10 30-60 Touchgama 3-6 20-30 Fusimotor, spindlesdelta 2-5 20-30 Sharp pain

B <3 5-15 Autonomic, pregangl.C <1.3 0.5-2 Slow painNon myelinated

The Peripheral Nervous System

• Motor: weakness, atrophy

• Sensory loss– Large Fibers (position)– Small fiber (pain)

• Reflex loss• Autonomic symptoms– (redness, dizziness)

Definitions

• NeuropathyPathological process affecting a peripheral nerve/s

• MononeuropathyA single nerve affected

• Mononeuritis multiplex Multiple mononeuropathy or Multifocal neuropathy

Cont..• Polyneuropathy• Diffuse symmetrical disease usually• beginning peripherally• Acute/Chronic Static/Prog• Relapsing/Recovering• Motor Sensory• Sensrimotor(Mixed) • Autonomic• Demyelinating Axonal

• Radiculopathy Nerve root disease

Mechanisms of damage:• Demyelination Myelin sheath disrupted

GBS Post Diphtheric HSMN

• Axonal degeneration Axon damage Toxic neuropathies

• Wallerian degeneration Nerve section

• Compression Focal demyelination Entrapment-Carpel tunnel syndrome

• Infarction ArteritisPolyarteritis nodosa Churg-Strauss synd. DM

• Infiltration Infiltration Leprosy Sarcoidosis

Cont…

EXAMINATION FINDINGS• Purely Motor or Sensory or Sensorimotor?• Proximal or distal? Symmetric or asymmetric?

• Multifocal, generalized, regional?• Upper limbs, lower limbs, neck, trunk?

TIMING• Acute or chronic?

Cont…• ASSOCIATED FINDINGS• Painful or painless?• Hereditary or sporadic?

• ELECTRODIAGNOSIS• Axonal or demyelinating?• LABORATORY• Paraprotein present? Type?• Antibody against nerve?• CSF protein level?

• HISTOLOGY• Inflammatory Cells

Mononeuropathy (Involving Single Nerve)– Carpal Tunnel Syndrome– Facial Neuropathy– Ulnar Neuropathy etc

Mononeuropathy Multiplex (Multifocal dysfunction; asymmetrical process involving two or more nerves).

• Polyneuropathy (Involving more than 2 Nerves)– TOSS– Polyradicuopathies– AIDP– CIDP etc

Autonomic Neuropathy:Dysfunction of Autonomic Neurons with consequent:o Anhidrosis or Hyperhidrosiso Orthostatic Hypotension,o Pupillary Reflex Paralysis,o Loss of Lacrimation & salivation,o Bowel & Bladder Dysfunction etc

mostly occur with generalized Polyneuropathy i.e. DM, Riley-Day Syndrome (Autosomal Recessive Disease) also called as

“Familial Dysautonomia”. Shy-Drager Syndrome

Clinical assessment Sensory Symptoms

• A sensation of wearing an invisible "glove" or "sock" • Numbness, pins & needles• Feeling of walking on pebbles• Feeling of tightness & swelling• Burning sensation or freezing pain • Sharp, jabbing or electric shock-like pain • Extreme sensitivity to touch • Usually worse at night • Loss of balance and coordination • Cramps in the feet and calves

Motor Symptoms

• Tripping on the toes• Loss of grip strength• Ankle jerk reflex is classically absent in

peripheral neuropathy.

Clinical Examination & Assessment

Signs:

Weakness: Usually distal & symmetrical in polyneuropathy Muscle Atrophy: Loss of muscle bulk, reduced tone and flaccidity Sensory Deficit: Varies with somatotopic distribution Areflexia: Loss of reflexes in Lower motor neuron lesions (LMNLs)

while Hyperreflexia in Upper motor neuron lesions (UMNLs).

Seddon classification:

Sunderland’s classification:

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