Oxford / Bamford Classification

Introduction

• The Oxford Community Stroke Project classification of sub-types of cerebral infarction devised by Bamford and colleagues is a useful descriptor for stroke subtypes that is both prognostically and aetiologically useful.
• Bamford and colleagues used data from the Oxford Community Stroke Project to define four sub-categories of cerebral infarction on the basis of presenting symptoms and signs: lacunar infarcts (LACI); total anterior circulation infarcts (TACI); partial anterior circulation infarcts (PACI); and posterior circulation infarcts (POCI). The classification is based upon bedside clinical features.
• The labels however are anatomical, and the symptoms and signs help localise the signs and site of cerebral infarction. A patient with a POCI has the best chance of a good recovery, and patients with a LACI the best chance of survival. Although their work was predominantly on infarcts the classification can be used for haemorrhage once the imaging has identified the stroke type.

Anterior vs Posterior Circulation

• Simply put the front of the brain is supplied by the right and left internal carotid arteries. The brain supplied by the internal carotids is called the "anterior circulation". The back of the brain (brainstem/cerebellum and occipital lobes and thalamus) is supplied by the vertebral arteries and this is called the posterior circulation.
• This is how we get the classification. An anterior circulation stroke therefore implies that it didn't involve the vertebrobasilar system. Posterior circulation strokes imply that there was no involvement of the carotid arteries.

Classification

• Lacunar infarcts (LACI): any of these
  • Pure motor stroke
  • Pure sensory stroke
  • Sensori-motor stroke
  • Ataxic hemiparesis
  • Must not have higher cortical function loss - dysphasia or neglect
• Total anterior circulation infarcts (TACI): Must have 3 of 3 of
  • Higher cerebral dysfunction (e.g. dysphasia)
  • Homonymous visual field defect
  • Ipsilateral motor and/or sensory deficit of at least two areas (out of face, arm and leg).
• Partial anterior circulation infarcts (PACI): Only 2 of 3 components of a TACI, or with higher cerebral dysfunction alone, or with a motor/sensory deficit more restricted than those classified as LACI (e.g. confined to one limb). Must have 2 of 3 of or dysphasia/neglect alone
  • Higher cerebral dysfunction (e.g. dysphasia)
  • Homonymous visual field defect
  • Ipsilateral motor and/or sensory deficit of at least two areas (out of the face, arm and leg).
• Posterior circulation infarcts (POCI): Any of:
  • Ipsilateral cranial nerve palsy with contralateral motor and/or sensory deficit
  • Bilateral motor and/or sensory deficit
  • Disorder of conjugate eye movement
  • Cerebellar dysfunction
  • Isolated homonymous visual field defect.

Summary table

When talking about stroke side we are talking about the side of the pathology NOT the side with clinical symptoms and signs. A left TACS therefore has Right hemiparesis(weakness), right hemi-sensory loss, right homonymous hemianopia and dysphasia

Assessment

The easiest way to use the Bamford classification is to look for the presence or absence of the four main features of stroke described above

• Hemiparesis or Hemisensory loss which are regarded as equal in Face/Arm/Leg
• Higher cortical dysfunction (including language problems)
• Homonymous hemianopia
• Brainstem signs: Vertigo, dysphagia, diplopia, cerebellar signs

The type of stroke is then coded by adding a final letter to the above after the CT scan has shown the cause

• I - for infarct (e.g. TACI)
• H - for haemorrhage (e.g. TACH)
• S - for syndrome; intermediate pathogenesis, prior to imaging (e.g. TACS)

References

• A prospective study of acute cerebrovascular disease in the community: the Oxfordshire Community Stroke Project 1981-86. 1. Methodology, demography and incident cases of first-ever stroke.J Neurol Neurosurg Psychiatry. 1988 Nov; 51(11): 1373-1380.