Neurology: Cranial Nerves and Sensory Impairment

Study Notes

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.

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).

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.

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.

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.

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

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.

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.