Clinical diagnosis

Misdiagnosis of stroke is common: 20% of emergency department diagnoses may be incorrect, and 10% of stroke unit patients are discharged with an alternative diagnosis. Many common misdiagnoses are characterised by global rather than focal cerebral dysfunction (sepsis, hypoglycaemia, drug overdose, and metabolic disturbance all being common). These problems attest to major and basic deficits in public and non-specialist medical knowledge of the characteristics of stroke. Many misdiagnoses are serious and treatable conditions. Some common neurological differential diagnoses require prompt treatment (for example, seizure, brain tumour, subdural haematoma) while more benign conditions (for example, Bell's palsy, peripheral nerve pressure palsies) are important largely in order to avoid unnecessary treatment. Uncommon neurological disorders often cause diagnostic difficulty to non-neurologists: for example, when faced with “progressing brainstem stroke” it is wise to consider Miller Fisher syndrome or myasthenia gravis.

Pertinent features of the clinical examination are usefully summarised by the test items included in the US National Institutes of Health stroke scale (see box below), and a syndromic classification derived from the Oxfordshire community stroke project (OCSP) is clinically useful with respect to aetiology and prognosis (table 1). However, the accuracy of OCSP classification is limited in the first 24 hours after onset, and diffusion weighted magnetic …