Peripheral Neuropathy Overview

Peripheral Neuropathy

• Defined as degeneration or inflammation of peripheral nerves, leading to impaired nerve function.
• Classified according to the number of affected nerves:
  • Mononeuropathy: Affects a single nerve.
  • Mononeuritis Multiplex: Affects multiple nerve trunks asymmetrically.
  • Polyneuropathy: Affects all peripheral nerves symmetrically.
• Types of Peripheral Neuropathy include:
  • Mononeuropathy
  • Polyneuropathy
  • Mononeuritis multiplex
• Polyneuropathy can be further classified by onset, pathology, nerve type affected, and etiology:
  • Onset: Acute (Guillain-Barré syndrome), Chronic (hereditary polyneuropathy)
  • Pathology: Demyelination, Axonal
  • Nerve type: Motor, Sensory, Autonomic, Mixed
  • Etiology: (see below)
• Clinical presentation can include motor, sensory, and autonomic manifestations.
  • Motor: Lower Motor Neuron Lesion (LMNL)
  • Sensory: Stocking and glove hyposthesia, and deep sensory loss.
  • Autonomic: Brittle nails, loss of hair, trophic ulcers
• Types of Peripheral Neuropathies:
  • Peroneal muscle atrophy (Hereditary motor and sensory neuropathy): Characterized by gradual onset, progressive course, starting in the first or second decade of life. Wasting and weakness in the lower limbs take a shape of inverted champagne bottle. Stoke and glove anesthesia and skeletal deformities (e.g., pes cavus) occur.
  • Refsum's disease: Hereditary familial type. Deficient phytanic acid hydroxylase enzyme leads to gradual onset and progressive courses. Symptoms start in the first/second decade of life. Other symptoms are hypertrophic neuropathy, retinitis pigmentosa, deafness, ichthyosis, and skeletal deformities. Treatment includes dietary restriction, and plasmapheresis if needed
  • Metabolic Peripheral Neuropathy - Commonly seen in diabetes mellitus. Can present as mononeuropathy, mononeuritis multiplex, or polyneuropathy. Often polyneuropathy is mainly sensory and autonomic. Sometimes it can be manifested by motor symptoms. Treatment includes controlling diabetes, vitamin B12, and symptomatic treatment for neuropathic pain.
  • Post-infectious neuropathy (Guillain-Barré syndrome): Pathogenesis involves cross-reactivity of antibodies aimed at the viral infection targeting myelinated nerve fibers. Shows acute onset of quadriparesis (proximal > distal). Cranial nerve affection (bulbar, bilateral facial) can be present. EMG shows demyelinating polyneuropathy. CSF analysis demonstrates cytoalbuminous dissociation. Treatment is centered on respiratory care, bed rest, plasmapheresis, or IV immunoglobulin (IVIg), and physiotherapy.
  • Infectious neuropathy (e.g., diphtheria, leprosy):
    • Diphtheria: Exotoxin of Corynebacterium diphtheriae. Presents 2-8 weeks post-infection with descending motor neuropathy. Treatment using anti-diphtheric serum.
    • Leprosy: Mycobacterium leprae. Sensory neuropathy. Affects lateral popliteal, ulnar, and trigeminal nerves. Treatment includes dapsone and rifampicin.
  • Nutritional neuropathy (e.g., pellagra, beri-beri):
    • Pellagra: Niacin deficiency (deficient dietary intake or increased demands or parasitic infections). Clinical presentation includes dermatitis, diarrhea, and neurological manifestations (dementia, paraplegia, polyneuropathy). Treatment: intravenous nicotinamide.
    • Beri-beri: Thiamine deficiency affecting the nervous system (dry beri-beri) or cardiac system (wet beri-beri). Dry beri-beri presents with sensory polyneuropathy. Wet beri-beri causes congestive heart failure. Cerebral type shows Wernicke’s encephalopathy. Treatment using thiamine 100 mg daily.
    • Subacute combined degeneration of spinal cord: Vitamin B12 deficiency causes this. Possible causes are deficient intake, intrinsic factor deficiency (pernicious anemia, atrophic gastritis), malabsorption syndrome, increased demands, and hepatic failure. Clinical signs include megaloblastic anemia, gastrointestinal manifestations (stomatitis, nausea, vomiting, diarrhea), and neurological manifestations (sensory neuropathy, deep sensory loss, pyramidal tract affection). Treatment includes replacement of vitamin B12.

Classification of Polyneuropathy

Etiological Classifications of Polyneuropathy

Clinical Picture

• Clinical picture of peripheral neuropathy is classified into motor, sensory and autonomic manifestations.

Types of Peripheral Neuropathy

• Includes individual conditions such as Peroneal muscle atrophy and Refsum's disease (with specific etiologies, features and methods of treatment).

Investigations

• EMG and nerve conduction studies (NCS) can identify the type of neuropathy (demyelinating or axonal).
• Other investigations depend on suspected causes (e.g., fasting blood sugar, serum vitamin levels, serum phytanic acid level).

Causes of Specific Types of Neuropathy

• Causes of motor, sensory, and thickened nerves are described.

This quiz delves into the definition, classification, and types of peripheral neuropathy. You will learn about the different forms of nerve impairment, including mononeuropathy and polyneuropathy, along with their clinical presentations and classifications. Test your knowledge on this important aspect of neurological health.