Neuritis is the term for inflammation of the nerve. It may be due to a number of causes including mechanical trauma, chemical injury, nutritional deficiencies, infections, inherited disorders and systemic diseases. Inflammation of a sensory nerves may present with numbness, tingling, abnormal sensations or pain. When the motor nerves are affected, symptoms may involve muscle weakness or even paralysis in severe cases. Some nerves are mixed nerves meaning that both sensory and motor fibers are affected leading to a complex of symptoms. Since the symptoms of neuritis are non-specific for the cause, various diagnostic investigations may first have to be considered. Treatment would then depend on the causative factor and underlying diseases.
Diagnosis of Neuritis
The primary objective of measures adopted for diagnosis of neuritis is to identify the cause of the neuritis. This provides important information regarding whether the neuritis can be treated or not. Some types of neuritis can be cured but others can only be managed to provide symptomatic relief.
The diagnosis of neuritis requires complete medical history and complete physical examination with detailed neurological examination. Several sets of investigations are also useful in diagnosis of neuritis.
Blood tests may be conducted to detect the following :
- Infections and inflammation – CBC, ESR, antibodies (infections)
- Diabetes mellitus – GTT, HbA1C
- Nutritional deficiencies - B-group of vitamins
- Autoimmune diseases – antinuclear antibodies (ANA)
Eye Tests for Optic Neuritis
- Eye tests for color vision and visual acuity.
- The fundus of the eye is visualized for examining the edema or inflammation of the optic disc using fundoscope or indirect ophthalmoscope.
- Light reflex is tested to check the reaction of the pupil to bright light.
- Visual response tests are performed to detect the damaged areas of the optic nerve.
A lumbar puncture will allow for analysis of the cerebrospinal fluid (CSF) in patients with suspected encephalitis or meningitis.
Nerve conduction tests and Electromyography (EMG)
Electrodiagnostic studies are generally used to confirm neuropathies.
- Nerve conduction test are used to check electrical function of peripheral nerves by measuring strength and speed of nerve signals transmitted. It also helps in localization of the affected part of the nerve.
- Electromyography (EMG) is a useful diagnostic test in patients with neuritis involving the motor nerves where there are symptoms of muscle weakness or paralysis.
A nerve biopsy is not a routine test but may be done in a select group of patients to confirm the diagnosis. A small sample of the affected nerve is biopsied and examined by a pathologist. The biopsy allows for the detection of physical changes in and around the nerve.
Radiological studies (MRI, CT scan or X-ray) are of importance in neuritis resulting from compression or trauma of the nerve. It is also useful in identifying tumors and granulomatous lesions in conditions like sarcoidosis. More importantly, radiological studies are used to exclude other diseases that may mimic neuritis.
Treatment of Neuritis
The most effective approach to treatment and management of neuritis is to identify the cause and treat it accordingly. Treatment for neuritis on its own is limited and if the causative factor cannot be removed or managed, then symptomatic treatment may be the only remaining option.
Drug therapy for neuritis itself, and not an underlying cause, is limited. It is primarily intended for neuropathic pain and depends on the severity of the pain. Medication may also provide short term relief for the other symptoms of neuritis.
- Mild pain may respond to NSAIDS (acetaminophen, aspiring) or codeine.
- Moderate to severe pain may require opioid analgesics like tramadol, hydrocodone or oxycodone drug combinations.
- Acute pain may require the use of corticosteroids although this has a minimal role in chronic neuropathic pain.
- Other symptoms of neuritis like abnormal sensations may be relieved in the short term by corticosteroids. It is also one of the best options for patients with optic neuritis as it prevents the loss of vision.
Chronic Neuropathic Pain
The medication for symptomatic pain relief in patients with chronic neuropathic pain includes :
- Duloxetine which is useful in treating chronic nerve pain and pain associated with shingles or diabetic peripheral neuropathy.
- Pregabalin is used to treat neuropathic pain associated with diabetic neuropathy.
- Amitriptyline is an antidepressant drug useful in neuropathic pain.
- Carbamazepine and other antiepileptics are commonly used in management of neuropathic pain. Carbamazepine is known to suppress the bone marrow causing leukopenia (low white blood counts) and necessitates blood count monitoring in patients.
- Capsaicin creams are popular topical medications for neuropathic pain. Use of topical capsaicin is associated with a mild burning sensation which acts like a counter-irritant to provide relief from the pain.
- Lidocaine and other local anesthetics are only considered for severe unbearable neuropathic pain. It may be administered as a topical application or injections.
Neuritis patients with involvement of motor nerves may benefit from physical therapy. The affected muscles are mobilized to maintain the full range of motion of both the muscles and associated joints. Physical therapists may use a number of modalities including :
- Heat application
- Cold therapy
- Transcutaneous electrical nerve stimulation (TENS)
- Acupressure / trigger point therapy
- Acupuncture / dry needling
Passive and active exercises may be advised as soon as possible.
Dietary modification and nutritional supplementation are considered in cases of neuritis associated with deficiencies. Neuritic pain, numbness, weakness and other symptoms related to nutritional deficiency can be relieved with supplementation of a number of micronutrients.
- Vitamin B12 promotes growth of the nerves and its regeneration.
- Thiamine (vitamin B1) helps in healing of nerve injuries and reduces the symptoms of neuritis.
- Calcium and magnesium are important in nerve impulse conduction
- Lecithin is important to nerve protection and repair.
- Protein, a macronutrient, is also important in nerve repair and function.
The role of surgery in the treatment of neuritis is limited. Surgery is of value in neuritis related to nerve compression or physical injury. Various procedures may also be performed in the advanced stages of neuritis where medical management is not effective. Surgical denervation procedures may be done in patients suffering from extreme neuropathic pain.