ANSWER 46
The acute onset of these symptoms and signs with drowsiness in a 17-year-old girl raise
the possibility of a drug overdose. Her father is epileptic and is likely to be taking anti-
convulsants. The most likely explanation is that this patient has taken a phenytoin over-
dose, tablets which her father uses to control his epilepsy. She has taken an overdose as a
result of concern about her imminent exams. Excessive ingestion of barbiturates, alcohol
and phenytoin all cause acute neurotoxicity manifested by vertigo, dysarthria, ataxia and
nystagmus. In severe cases coma, respiratory depression and hypotension occur.
Vertigo is an awareness of disordered orientation of the body in space and takes the form
of a sensation of rotation of the body or its surroundings.
Peripheral lesions Central lesions
Benign positional vertigo Brainstem ischaemia
Vestibular neuronitis Posterior fossa tumours
Ménière’s disease Multiple sclerosis
Middle-ear diseases Alcohol/drugs
Aminoglycoside toxicity Migraine, epilepsy! Causes of vertigo
The duration of attacks is helpful in distinguishing some of these causes of vertigo. Benign
positional vertigo lasts less than 1 min. Attacks of Ménière’s disease are recurrent and last
up to 24 h. Vestibular neuronitis does not recur but lasts several days, whereas vertigo due
to ototoxic drugs is usually permanent. Brainstem ischaemic attacks occur in patients with
evidence of diffuse vascular disease, and long tract signs may be present. Multiple sclero-
sis may initially present with an acute attack of vertigo that lasts for 2–3 weeks. Posterior
fossa tumours usually have symptoms and signs of space-occupying lesions. Acoustic neu-
romas often present with vertigo and deafness. Migrainous attacks are often accompanied
by nausea and vomiting. Temporal lobe epilepsy may also produce rotational vertigo, often
associated with auditory and visual hallucinations. Central lesions produce nystagmus
which is multidirectional and may be vertical. Peripheral lesions induce a unilateral hori-
zontal nystagmus.
The diagnosis in this case can be made by measuring plasma phenytoin levels and by ask-
ing the patient’s father to check if his tablets are missing. Gastric lavage should be carried
out if it is within 12 h of ingestion of the tablets. Oral activated charcoal may be useful.
National poisons information services are available to advise on treatment. Before dis-
charge she should have counselling and treatment by adolescent psychiatrists.
- Vertigo can be caused by a variety of neurological disorders.
- A careful history and examination may reveal the cause of vertigo.
- Overdose should be considered in any patient presenting with decreased conscious
level and respiratory depression.