Coma and Stupor

Coma and Stupor

·        Checking eyes:

o   Doll‟s Eye: do eyes remain fixed on target when head is turned. Tests inputs from the neck muscles. Requires linking via medial longitudinal fasiculus of nerves 3, 4, and 6 on both sides

o   Vestibulo-Ocular reflexes: caloric response. 1 ml of ice water evokes nystagmus beating to the opposite side in a normal person. If unconscious, see only deviation without corrective nystagmus

o   In deepening diffuse coma without structural damage, the Dolls eye disappears, then the Caloric response. If pupils still reactive then no coning

Due to Structural damage

·        Only if affecting brain areas required to maintain consciousness: usually infarct, bleed or inflammation

·        Reticular Activating System: periventricular grey matter from mid pons up, including the hypothalamus and deep grey matter of both hemispheres

·        Most supra-tentorial lesions produce coma due to oedema ® compression of deep hemispheric structures (paramedian diencephalon)

·        Features of coning:

·        Transtentorial: progressive drowsiness followed by pupil changes

o   If unilateral cerebral swelling then stretching of ipsilateral 3^rd nerve ® ¯parasympathetic innervation

o   If diffuse bilateral swelling involving brain stem then impairment of both sympathetic and parasympathetic ® mid position, irregular pupils

·        Posterior fossa coning: headache, stiff neck, ­BP, ¯pulse

Due to Diffuse depression of brain function

·        Usually metabolic encephalopathy

·        Key differential from structural damage: Pupillary reflexes retained

·        Features: clouded consciousness, difficulty concentrating, altered sleep wake patterns

·        Two basic types:

o  Delirium or acute toxic psychosis: agitated, hallucinatory, severely disorientated

o  Acute confusional state: quieter than delirium

·        Immediate evaluation: Glucose, thiamine, Na, Ca, Creatinine, pH, PO₂, PCO₂, lumbar puncture, sepsis (septicaemia, lung, urinary tract, meningitis)

·         Later: LFT, Sedatives, Blood and CSF culture, Electrolytes and Mg, Coagulation, EEG (absence status)

·        Outcome:

o  Sedative drug poisoning: equivalent to GA and will recover with treatment

o  Other medical causes: depends on cause, severity and extent. Only 15% make a good recovery if in coma for more than a few hours

o  Traumatic: better outlook, related to age, 50% die (many instantly), if ophthalmologic signs of brain stem dysfunction then 90% die or remain vegetative