Neurological Disorders: Neuropathy

Introduction

Neuropathy is the medical term used for any kind of injury, damage or pathology of a nerve, in otherwords this is the term used for the diseases of the nerves. There are various types depending upon what causes it. This is one of the frequent Neurological disorders, and a Neurologist commonly involves in the care of these patients.

Basic Anatomy & physiology of the nerves

Nerves connect the peripheral structures like skin, muscle etc with the central nervous system (spinal cord & brain). They are composed of bundles of miscroscopically thin nerve fibers. If the fibers carry nerve signals from the spinal cord/brain towards the periphery (e.g. muscle) they are called as motor nerves, and if from the periphery towards the spinal cord and brain then they are called as sensory nerves. Many nerves are actually of mixed type, means they carry both type of sensation through them.

Many nerves also carry fibers belonging to autonomic nervous system. This system deals with the control of involuntary body system like, digestive, heart, blood pressure, secretion from various glands, sweating, bladder, bowel function etc.

Classification of nerve diseases

Based on the pattern of nerve involvement:

• Mononeuropathy: Only a single nerve is affected; e.g. carpal tunnel syndrome.

• Polyneuropathy: Multiple nerves are involved especially in a diffuse and symmetrical fashion in both limbs; e.g. diabetic polyneuropathy.

• Mononeuritis multiplex: Multiple nerves are involved, but randomly (asymmetrically) on both sides rather than symmetrically; e.g. vasculitis related.

Based on type of sensory nerve fibers involved:

Large diameter fiber versus small fiber types

Autonomic versus non autonomic types etc.

The sensory nerve fibers within each nerve are of two types; large and small diameter fibers. The large diameter fibers carry sensation like vibration, joint position sensation etc. The smaller fibers carry sensation like pain, temperature etc. Autonomic fibers are also a type of small fibers.

Based on the rapidity of evolution of the symptoms

Acute type: GBS (Guillain Barre syndrome)

Subacute or chronic type: Diabetic, hereditary types (CMT etc).

What causes nerve diseases?

There are myriad causes including;

• Congenital (born with that)
• Traumatic
• Nutritional deficiency (e.g. Vitamin B12 deficiency)
• Nutritional excess (e.g. high dose Vitamin B6 chronic usage)
• Genetic (e.g. Charcoat Marie Tooth disease or CMT)
• Metabolic / Endocrine disorders (e.g. Diabetes mellitus)
• Toxin exposure (e.g. chronic alcohol consumption)
• Compresive (e.g. CTS or carpal tunnel syndrome)
• Infections (e.g. AIDS virus)
• Inflammatory conditions (e.g. lupus or SLE) etc.

How does patient manifest?

• Numbness
• Tingling (pins & needles)
• Loss of sensation in the limbs, especially distally (feet & hands)
• Hyperesthesia (abnormally exaggerated sensory feeling)
• Allodynia (non pain stimulus felt as pain)
• Muscle weakness
• Muscle atrophy (thinning)
• Tropic skin changes (e.g. dryness, hair loss etc)
• Gait ataxia (unsteadiness)
• Bladder and/or bowel disturbances etc.

Some very common nerve disease conditions

• Diabetic polyneuropathy
• Alcoholic polyneuroathy
• CTS (carpal tunnel syndrome) etc.

Diagnosis

If the history is clear and presentation is typical then only few investigations may be sufficient otherwise a bunch of neurology tests are generally needed and such tests include;

• Blood tests like vitamin B12, folate, thyroid tests, ESTR/CRP,ANA serum protein electrophoresis, HIV test etc
• EMG/NCS (electromyography and nerve conduction studies)
• CSF (cerebrospinal fluid) analysis
• Nerve biopsy
• Genetic tests etc

Not every patient requires each & every tests.

Treatment

Treatment is both symptomatic & specific. The specific treatment would depend upon the type of nerve disease. For example if vitamin B12 deficiency is the cause then B12 supplementation is given; for AIDP immunoglobulin and/or plasmapheresis may be required.

Symptomatic treatment would include medication for nerve pain, numbness, tingling like sensation and includes medications like gabapentin, duloxetine etc. Physical therapy is given if muscle weakness is present.

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