Neurology: Bell's Palsy Overview

Bell's Palsy

• Bell's palsy is an acute, idiopathic, unilateral facial nerve palsy (cranial nerve VII).
• It's thought to be caused by reactivation of herpes simplex virus (HSV)-1.
• Clinical features often include taste dysfunction, reduced hearing, increased tearing (due to weakness of orbicularis oculi and lacrimal gland dysfunction), and vesicles in the ear or on the palate (if caused by herpes zoster).
• Treatment with prednisolone (40-60mg daily) for a week can speed recovery if given within 72 hours.
• Approximately 80% of patients recover spontaneously within 12 weeks.

Central Lesion (Supranuclear Facial Palsy)

• Characterized by contralateral weakness on the lower half of the face.
• Patients cannot smile, their mouth droops to the affected side.
• They cannot fully open their mouth, and have a flattened nasolabial fold.
• Forehead wrinkling and eyebrow raising are possible.
• Eyes close normally, and Bell's phenomenon is absent.
• Taste and hearing are unaffected.
• Facial reflexes are increased, and there's no facial muscle atrophy.

Peripheral Lesion (Infranuclear Facial Palsy)

• Causes ipsilateral weakness of the entire affected hemi-face.
• Mouth droops to the paralyzed side with difficulty smiling.
• Mouth opening, nasolabial fold, and forehead/eyebrow movements are impaired.
• Eyes don't close properly; Bell's phenomenon is present.
• Taste is affected (if the chorda tympani nerve is involved).
• Hearing may be affected (if the nerve to stapedius is involved).
• Facial reflexes are normal, but there is facial muscle atrophy.

Carpal Tunnel Syndrome

• The most common entrapment neuropathy, resulting from median nerve compression at the wrist's carpal tunnel.
• Often bilateral and more frequent in women.
• Risk factors include pregnancy, hypothyroidism, amyloidosis, diabetes mellitus, acromegaly, and arthritis, as well as repetitive wrist motions.
• Symptoms include nocturnal pain, numbness, and paraesthesia in thumb, index, middle, and radial side of ring finger.
• Ape hand appearance, difficulty opposing thumb and little finger, and pain reproduced with wrist flexion (Phalen sign) or tapping the median nerve (Tinel's sign) are common.
• Treatment initially involves wrist splints and NSAIDs; steroid injections may be required if symptoms persist.

Guillain-Barre Syndrome (GBS)

• Acute, rapidly progressive, acquired demyelinating autoimmune disease of peripheral nerves.
• Most of the cases are related to Campylobacter jejuni infections.
• It presents with symmetric ascending paralysis, loss of deep tendon reflexes, facial and bulbar weakness, and respiratory weakness requiring ventilator support (in 20% cases).
• Autonomic dysfunction (orthostatic hypotension, arrhythmia, and sweating) can also occur.
• Diagnosis involves assessing CSF findings (elevated protein with normal cell count), electromyography (showing decreased conduction velocity), and clinical presentation.
• Management includes regular monitoring of respiratory function, ventilation if vital capacity falls below 1 L, and plasmapheresis or intravenous immunoglobulin (IVIG) within the first 14 days.

Myasthenia Gravis

• An autoimmune disease caused by antibodies against post-synaptic acetylcholine receptors.
• Characterized by asymmetric muscle weakness that worsens with activity and improves with rest.
• Ptosis (drooping eyelids) and diplopia (double vision) are common initial symptoms, often related to extraocular muscle fatigue.
• Deep tendon reflexes are typically normal, while papillary response and sensory abnormality are absent or none.
• Most cases are more common in younger individuals (20-30 years), and less frequent in older individuals (60-70 years)
• Thymectomy can be a treatment option, especially in younger patients with thymoma or thymic hyperplasia.
• Diagnosis often includes a Tensilon test (edrophonium injection causing rapid improvement of symptoms), electromyography (showing decremental response to repetitive nerve stimulation) and blood tests for antibodies (AChR antibodies).
• Treatment often involves anti-cholinesterase agents (pyridostigmine) initially. Immunologic treatments like IVIg or plasmapheresis are used for acute crises, and immunosuppressants (e.g., azathioprine, cyclophosphamide) in chronic cases.
• Myasthenic crisis (severe weakness) or cholinergic crisis (overdose of anticholinesterase drugs) can complicate the condition.

Lambert-Eaton Myasthenic Syndrome (LEMS)

• An autoimmune disease where antibodies target presynaptic calcium channels in neuromuscular junctions.
• Often associated with small cell lung cancer (60% of cases).
• Key feature is proximal muscle weakness that improves with activity, and absence of deep tendon reflexes (DTRs) while DTRs return after sustained contraction of the muscle.
• Diagnosis involves electromyography (showing incremental response to repetitive nerve stimulation) and blood tests for antibodies to presynaptic calcium channels.
• Treatment may include 3,4-diaminopyridine or pyridostigmine, immunosuppressants, and treatment of the primary malignancy (if present).