Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 5, 2011, pp. 657-658

Neurology India, Vol. 59, No. 5, September-October, 2011, pp. 657-658

Editorial

The role of proton neurospectroscopy in the assessment of brain function, estimation of coma duration, and prediction of outcome in severe traumatic brain injury

Basant K Puri

Departments of Surgery and Cancer, and Imaging, Hammersmith Hospital and Imperial College London, United Kingdom
Correspondence Address: Basant K Puri, Department of Imaging, Hammersmith Hospital, Du Cane Road, London W12 0HS, England, United Kingdom, basant.puri@imperial.ac.uk

Date of Submission: 04-Oct-2011
Date of Decision: 04-Oct-2011
Date of Acceptance: 04-Oct-2011

Code Number: ni11205

PMID: 22019645

DOI: 10.4103/0028-3886.86535

Traumatic (or closed) brain injury has an annual incidence in the United States of approximately 150 per 100,000, more commonly affects males, and is often the result of motor vehicle accidents (particularly in those aged 15 to 24 years in the USA) and of falls (particularly in those aged over 64 years). ^[1] In 1974, Graham Teasdale and Bryan Jennett, from the Glasgow University Department of Neurosurgery, published the Glasgow Coma Scale. ^[2] They developed this scale on the basis that in gauging change (deterioration or improvement) in the acute stage of a condition associated with coma or impaired consciousness, and in predicting the ultimate outcome, 'the degree and duration of altered consciousness usually overshadow all other clinical features in importance. It is therefore vital to be able to assess and to record changing states of altered consciousness reliably.' ^[2] In order to achieve this, the Glasgow Coma Scale rates the following three aspects of behaviour: eye opening (scoring 1 for nil to 4 for spontaneous); best motor response (1 for nil to 6 for obeys commands); and verbal response (1 for nil to 5 for oriented); a total score of up to eight (inclusive) is considered to correspond to a severe injury, scores between nine and 12 to a moderate injury, and score between 13 and 15 (inclusive) to a mild injury. ^[1],[2]

In the years since the development of the Glasgow Coma Scale, the non-invasive technique of proton neurospectroscopy (¹H-Magnetic resonance spectroscopy of the brain) has become available clinically in centres having a magnetic resonance imaging (MRI) scanner. This technique affords the clinician a window into the chemistry of the living brain. Resonances can usually readily be assigned to N-acetylaspartate (NAA), an amino acid derivative thought to be located in neurones, choline-containing compounds (Cho) such as phosphoryl- and glycerophosphoryl-choline which participate in membrane synthesis and breakdown, and creatine and phosphocreatine (Cr). ^[3] Since NAA is a neuronal marker, its level may be expected to be diminished in proportion to the level of neuronal damage. Conversely, with the reverse process, the NAA level would be expected to increase, as for example has been found to occur in the primary motor cortex following recovery from partial spinal cord injury. ^[4] With increased neuroglial membrane breakdown following head injury, the Cho level would be expected to increase, again in proportion to the level of damage; such an increase has been reported, for example, in myalgic encephalomyelitis, in which an increase in the ratio of membrane phospholipid catabolism to anabolism may be associated with viral infection. ^[5]

The above proton neurospectroscopy findings hypothesized to occur in traumatic brain injury are reported in this issue of Neurology India, in a paper entitled '¹ H-magnetic resonance spectroscopy correlates with injury degree severity and can predict coma duration in patients following severe traumatic brain injury'. ^[6] Not only does this study of 72 patients following severe traumatic brain injury report reduced NAA and increased Cho (both expressed as ratios to the relatively neutral Cr levels), but, at least as importantly, these neurospectroscopy metabolite findings correlate with Glasgow Coma Scale scores and indeed also the Glasgow Outcome Scores. The magnetic resonance sequences used to acquire these data are quick and relatively quiet. Thus proton neurospectroscopy appears to be a safe, non-invasive and fast method of assessing brain function, estimating coma duration and predicting outcome following traumatic brain injury.

An important clinical message from this important paper is that, in addition to the clinical measurement of the three parameters of eye opening, best motor response and verbal response for assessment using the Glasgow Coma Scale, clinicians should seek to obtain the neurospectroscopy measurements of the three resonances assigned to NAA, Cho and Cr. This should become a routine part of the assessment and follow-up of traumatic brain injury in all centres having ready access to an MRI scanner.

References

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