Neurology Quiz: Bell's Palsy and Facial Reflexes

Bell's Palsy

• Bell's palsy is an acute, idiopathic, unilateral facial nerve palsy (peripheral cranial nerve VII).
• It is thought to be caused by reactivation of Herpes simplex virus (HSV)-1.
• Clinical features include taste dysfunction, reduced hearing, increased tearing due to weakness of the orbicularis oculi and lacrimal gland dysfunction.
• Vesicles in the ear or on the palate might indicate herpes zoster rather than Bell's palsy.
• Treatment includes prednisolone 40-60mg daily for a week, given within 72 hours. Recovery is spontaneous in about 80% of patients within 12 weeks.

Central Lesion (Supranuclear Facial Palsy)

• Characterized by contralateral weakness on the lower half of the face.
• Difficulty smiling, drooping mouth to the paralyzed side, inability to fully open mouth, flattened nasolabial fold, can wrinkle forehead, raise eyebrows.
• Eye closure present, Bell's phenomenon absent.
• Taste and hearing not affected.
• Increased facial reflexes.
• No facial muscle atrophy.

Peripheral Lesion (Infranuclear Facial Palsy)

• Ipsilateral weakness of the entire hemi-face.
• Difficulty smiling, drooping mouth to the paralyzed side, inability to fully open mouth, flattened nasolabial fold, can’t wrinkle forehead, raise eyebrows.
• Eye doesn't close, eyeball rolls up, Bell's phenomenon present.
• Taste affected if chorda tympani is involved.
• Ipsilateral hyperacusis(nerve to stapedius).
• Normal facial reflexes.
• Facial muscle atrophy.

Carpal Tunnel Syndrome

• The most common entrapment neuropathy.
• Results from median nerve compression at the wrist within the carpal tunnel.
• More common in women and is frequently bilateral.
• Risk factors include pregnancy, hypothyroidism, amyloidosis, diabetes mellitus, acromegaly, and arthritis, and repetitive motions of the wrist.
• Clinical features include pain/numbness in the thumb, index, middle, and radial side of the ring finger (mostly nocturnal), ape hand appearance (thenar muscle atrophy), difficulty opposing thumb and little finger, pain reproduced by tapping over median nerve, or pain with wrist flexion.
• Treatment includes wrist splints and NSAIDs as initial therapy, followed by steroid injections if NSAIDs are ineffective.

Guillain-Barré Syndrome (GBS)

• Acute, rapidly progressive, acquired demyelinating autoimmune disease of peripheral nerves.
• Known as "acute inflammatory demyelinating polyradiculoneuropathy".
• Most common acute peripheral neuropathy.
• Pathogenesis: T-cell mediated immune response accompanied by segmental demyelination induced by activated macrophages, associated with infections like Campylobacter jejuni (most common), Cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae.

Clinical Findings: GBS (general)

• Symmetric ascending paralysis (distal to proximal).
• Loss of deep tendon reflexes.
• Respiratory weakness requiring ventilator support (20% cases).
• Facial and bulbar weakness.
• Autonomic dysfunction (e.g., orthostatic hypotension, arrhythmia, sweating).
• Diagnosis: Albuminocytologic dissociation (CSF protein elevated, but no rise in cell count), Electromyography (shows decreased conduction velocity).
• Management: Regular monitoring of respiratory function, ventilation if vital capacity falls below 1L, plasma exchange (plasmapharesis) or intravenous immunoglobulin (IVIG) within the first 14 days.

Myasthenia Gravis

• Autoimmune disease against post-synaptic acetylcholine receptors.
• Type II hypersensitivity reaction.
• Clinical features: asymmetric muscle weakness that worsens with activity and improves with rest, ptosis (drooping eyelids) and diplopia (double vision) are early symptoms.
• Signs include deep tendon reflexes normal, papillary response normal, sensory abnormality none, autonomic dysfunction none, and age group young (20-30 years) more common for women, old (60-70 years) more common in men.
• Associated with thymic hyperplasia (65%) and thymoma (15%).
• Diagnosis: Tensilon test—rapid improvement of symptoms (within 30 seconds) with edrophonium which is an anti-cholinesterase , Electromyography shows decremental response to repetitive nerve stimulation, and specific antibodies like acetylcholine receptor antibodies (AChRA) and anti-MuSK antibodies.
• Treatment: cholinesterase agents (e.g., pyridostigmine) as initial therapy, Immunologic treatments, Thymectomy.

Myasthenic Crisis

• Exacerbation of myasthenia gravis.
• Severe weakness, potentially lethal complications like respiratory failure and aspiration.
• Treatment: Immunosuppression with glucocorticoids, IVIG, or plasma exchange.

Cholinergic Crisis

• Overdose of anti-cholinesterase drugs.
• Muscle fasciculation, paralysis, pallor, sweating, excessive salivation, and constricted pupils.
• Treatment includes withdrawal of anti-cholinergic drugs and endotracheal intubation for respiratory paralysis (follow FVC).

Lambert-Eaton Myasthenic Syndrome (LEMS)

• Autoimmune disease targeting pre-synaptic calcium channels in the neuromuscular junction.
• Commonly associated with small cell lung carcinoma (60%).
• Clinical features include proximal muscle weakness that improves with activity but doesn't improve with rest (in contrast to Myasthenia Gravis), absence of deep tendon reflexes (DTRs), DTRs return after sustained muscle contraction.
• Diagnosis: Electromyography shows an incremental response (post-tetanic potentiation) to repetitive nerve stimulation, and autoantibodies to presynaptic calcium channels.