Neurology: Cranial Nerves and Sensory Impairment

Hemiplegia

• Hemiplegia can be classified into different levels: cerebral, subcortical, capsular, brain stem, and spinal cord.
• Cerebral lesions:
  • Hemiplegia is usually not complete, monoplegia is more common.
  • Weakness is contralateral.
  • Cloudiness of consciousness is common.
  • Contra lateral cortical sensory loss in involvement of the parietal lobe.
  • Convulsions may be focal or secondary generalized.
  • Higher mental functions disorders (e.g. aphasia, agraphia, and agnosia) occur in lesions affecting specific lobes, centers, or sites.

Subcortical Lesions

• Weakness is more extensive compared to cortical lesions.
• Hemiplegia is usually complete.
• Hemi hypothesia on the paralyzed side is common.
• UMN facial and hypoglossal on the same side of paralysis are common.

Brain Stem Lesions

• Hemiplegia is termed crossed hemiplegia.
• Characterized by hemiplegia on the opposite side of the lesion with LMN cranial nerves affection on the same side of the lesion.
• Midbrain syndromes: e.g. Weber's syndrome (ipsilateral 3rd cranial nerve lesion, crossed hemiplegia).
• Pons syndromes: e.g. Millard Gubler syndrome (ipsilateral 6th, 7th cranial nerves lesion, crossed hemiplegia).

Clinical Features

• Onset: usually sudden in hemorrhage, may be subacute in thrombosis, acute or sudden in embolic.
• Course: may be regressive.
• Weakness: usually affects one half of the body, UL and LL in equal degree or one may be affected more than the other.
• Weakness affects group of muscles, affecting fine movements more, distal muscles are more affected.
• Progravity muscles are more affected than antigravity muscles.

Muscles Tone

• In acute lesions, there is a shock stage lasting for 2-6 weeks, during which there is a complete loss of tone of the paralyzed side.
• After this stage, tone gradually returns and spasticity appears.
• In gradual lesions, spasticity develops from the start and affects the antigravity muscles more than progravity muscles.

Deep Tendon Reflexes

• In the affected limbs, deep tendon reflexes are exaggerated, and pathological reflexes and clonus may be elicited.
• In the shock stage, deep reflexes are lost or diminished.

Superficial Reflexes

• The most important is the +ve Babinski sign.
• Abdominal and cremasteric reflexes are lost on the affected side.

Gait

• Gait is usually circumduction.

Medullary Syndromes

• Wallenberg syndrome: ipsilateral Horner's syndrome, ataxia, 9, 10, 11th cranial nerves, and decrease sensation over the face; contra lateral hemianathesia.

Spinal Cord Lesions (Brown Sequard's Syndrome)

• At the level of the lesion:
  • Ipsilateral LMN weakness of muscles supplied by the affected segments.
  • Loss of reflexes mediated by the interrupted segments.
  • Loss of sensation (radicular) in the area supplied by the diseased segments.
• Below the level of the lesion:
  • Ipsilateral hemiplegia.
  • Ipsilateral deep sensory loss.
  • Contra lateral superficial sensory loss.

Differential Diagnosis

• Hypoglycemia.
• Demylinating disease (e.g. MS).
• Brain tumors: history of headache, papilloedema, seizures, blurring of vision, progressive course, with gradual onset.
• Chronic subdural hematoma: history of head injury, weeks up to years before, more drowsiness, confusion & headache than the focal deficits.
• Encephalitis: acute or subacute onset of fever, cloudiness of consciousness, convulsions, signs of meningeal irritation, higher mental function disorders.
• Brain abscess: history of fever, headache with signs & symptoms of increased ICT, focal deficits, with source of infections (e.g. mastoditis, OM, congenital heart diseases).
• Todd's paralysis: history of epileptic seizures of focal onset.
• Hysterical hemiplegia: usually occurs in young age, with no +ve data on examination.

General Investigations

• Rapid one: to diagnose stroke and discover mimics.
• In ER: Blood sugar → to exclude hypoglycaemia.
• CBC & coagulation profiles → hematological disorders.