Two simple tests and one complex disease
- 1Department of Neurophysiology, Liverpool Health Service, Sydney, New South Wales, Australia
- 2Ingham Institute for Applied Medical Research, Liverpool, New South Wales, Australia
- 3South Western Sydney Clinical School, the University of New South Wales, New South Wales, Australia
- Correspondence to Professor J M Worthington, Department of Neurology, Liverpool Health Service, Elizabeth Street, Liverpool, Sydney, NSW 2170, Australia;
- Received 11 September 2012
- Accepted 20 September 2012
Half the survivors of aneurysm related subarachnoid haemorrhage (aSAH) become dependent,1 and half of those described as functionally independent are said to have cognitive deficits which seriously impact on everyday life.2 ,3 In a previous issue of JNNP, Wong et al evaluated the relative utility of the Montreal Cognitive Assessment (MOCA) and Mini-Mental State Examination (MMSE) bedside screening tools 3 months after aSAH.4
Cognitive impairment is a devastating and common outcome after aSAH and should be incorporated in outcome assessment in aSAH research,2 ,3 especially where the deficits can be related to potential treatment targets. Unfortunately, a ‘gold standard’ battery of neuropsychological tests for each patient is not feasible in most clinical or research settings and many stroke survivors do not have the stamina to complete such demanding tasks.2 Bedside screening tools, such as the MMSE and MOCA, are practical alternatives, and their validation in SAH is important.
The authors have analysed the relationship between MOCA and MMSE test results and important patient characteristics, such as SAH grade, Glasgow Coma Score and delayed cerebral infarction. The two screening tests were also analysed against the outcomes of functional assessment with the modified Rankin Scale (mRS), Lawton Instrumental Activity of Daily Living Scale and Short Form-36.4
The study reports some striking findings. In 3 month aSAH survivors, able to give consent and complete testing, 40% had MMSE scores <27% and 73% had MOCA scores <26. Both tests correlated strongly with accepted functional outcome measures. Importantly, MMSE, MOCA and mRS were independently associated with delayed cerebral infarction, perhaps the most important therapeutic target in aSAH research. The mRS scores were also independently associated with the World Federation of Neurosurgeons subarachnoid grading performed on hospital admission.4
While some mortality and morbidity can be predicted from early clinical and radiological grading,3 additional brain injury will occur in about one-third of early aSAH survivors, after the bleeding has stopped and the aneurysm has been secured.5 The processes responsible for delayed brain injury, with resulting death, physical disability, cognitive impairment and lost quality of life years, are unique to SAH and poorly understood. They manifest as severe clinical deterioration and delayed cerebral infarction between 4 and 11 days after aSAH,5 and the delay to onset of injury offers an opportunity for intervention. Most relate delayed brain injury to medium and large artery vasospasm but delayed cerebral infarction occurs in many patients or in brain regions where there are no signs of vasospasm.6 With the likely exception of nimodipine,1 vasospasm has also proved to be a poor therapeutic target, leaving researchers to pursue other biological targets.
Wong et al have shown that cognitive impairment, determined by bedside MMSE and MOCA testing, is highly prevalent and correlates with the delayed cerebral infarction often seen after aSAH.4 In practical terms, the study suggests that any one of these two simple bedside cognitive tests would provide useful outcome measures in aSAH research. There may be additional value in determining the relative sensitivity and specificity of MMSE and MOCA against formal neuropsychological testing, but such comparisons can be analytically difficult2 and represent a major undertaking. In the meantime, the MOCA or MMSE deserves a place with the mRS.
Competing interests None.
Provenance and peer review Commissioned; not externally peer reviewed.