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Bridging the gap at a stroke

5 Feb, 2013

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A tale of two halves

A tale of two halves

“The patient is a 62-year-old professor of anatomy who was suddenly taken ill during a lecture-trip abroad.”

‘The patient’ is also the author in this rather wonderful paper by Professor Alf Brodal, published in the journal Brain 40 years ago. It is called ‘Self-observations and neuro-anatomical considerations after a stroke’.

“The present illness started suddenly when the patient woke up and turned in his bed on the morning of April 12, 1972. In the course of a few minutes an initial heavy, but uncharacteristic, dizziness was followed by dysarthria, double vision and a marked paresis of the left arm and leg. There was no loss of consciousness, no headache or vomiting and no stiffness of the neck. In the very beginning there were paræsthesiæ of the left side of the head, especially the scalp.”

Brodal’s first-hand account was cited in a more recent contribution to the scientific literature from a group of researchers including Janet Eyre, some of whose work we featured in our Focus on stroke series last year. In ‘The myth of the ‘unaffected’ side after unilateral stroke: Is reorganisation of the non-infarcted corticospinal system to re-establish balance the price for recovery?’, Eyre and her co-authors are particularly interested in Brodal’s description of the effect of the stroke on his handwriting.

The right side of the brain controls the left side of the body and vice versa. Brodal’s stroke occurred in the right side of his brain so, being right-handed, he hadn’t expected his writing to be affected: “[I]t came as a surprise to the patient that there were clear-cut changes in his handwriting after the stroke….

Samples of Brodal's handwriting after (above) and before (below) his stroke

Samples of Brodal’s handwriting after (above) and before (below) his stroke, taken from his 1973 paper.

“There was a tendency for the lines of writing to be uneven or oblique, not horizontal, and the distance between the lines were often uneven. The shape of the individual letters tended to be more irregular than previously, they were less smooth, and the last stroke in the writing (up or down) was sometimes missed or it was incomplete or exaggerated. Furthermore, there was often dropping out of one or two letters or of a word, or a letter which should be doubled was repeated three times (lettter instead of letter). More often than before figures were interchanged, for example he wrote 46 instead of 64. These changes in his writing gradually became less marked, but they could still be noticed more than nine months after the stroke.”

Brodal then spends several pages considering how damage to the right side of the brain could have an effect on the function of his right hand. A number of studies have followed over the decades, confirming the phenomenon but not fully explaining it. In December 2012, Eyre and her colleagues published evidence for at least part of the answer.

On balance

A stroke is caused by an interruption in the blood supply to the brain. It can be the result of a blood vessel becoming blocked (ischaemic stroke) or rupturing (haemorrhagic stroke). Either way, the result is that a part of the brain loses its blood supply and is rapidly damaged as a result. Often, the damaged area is entirely within one side of the brain, which leads to symptoms such as paralysis or weakness on only one side of the body.

But the brain is – to an extent – adaptable. After the initial ‘brain attack’, it can reorganise its neural circuits so as to bypass the damaged area as much as possible, rerouting connections between brain cells and restoring some of the functions that seemed to be lost or reduced just after the stroke occurred. However, such unilateral reorganisation of the brain would leave it in an ‘unbalanced’ state and it is possible that a lack of symmetry between the two sides of the brain hinders its ability to function. Eyre and colleagues propose that the undamaged side of the brain therefore also reorganises, to match as closely as possible the changes being made to repair the damaged side.

In their study, they report that stroke patients whose brains were more symmetrically organised (assessed at least 18 months after their stroke) tended to show better recovery. This suggests that the two sides of the brain reorganise in tandem. Even though this strategy can lead to additional impairment on the ‘unaffected’ side of the body – such as Brodal’s unexpectedly affected handwriting – the overall effect is usually positive.

The findings suggest that stroke patients require rehabilitation programmes that consider both sides of the body, even if the stroke itself only appears to have damaged one side of the brain. Leaving out the ‘unaffected’ side risks allowing additional impairments to develop as the brain tries to keep its balance while fixing the stroke damage.

Know thyself

Reading Brodal’s account of his own experiences of stroke, I was struck by two things: first, his sense of wonder and awe, even after a long and distinguished career as a neuroanatomist, at his own brain’s complexity and capacity to heal; and second, his experience of the psychological effects of a stroke:

“In addition to the changes mentioned which can be objectively studied, the patient has found that destruction of even a minor part of the brain causes changes in a number of functions which are difficult to study objectively. They are, however, very obvious to him.”

In general, such symptoms might include the loss of ability to concentrate, reduced short-term memory, fatigue, loss of motivation, depression and changes in personality. Stroke rehabilitation services are improving (thanks to research and the implementation of new tools, as I discovered last year) but it is still a significant challenge to identify and tackle these ‘hidden’ problems, which are often the most profound, debilitating and long-lasting effects of a stroke.

As Brodal put it:

“Even after ten months if the patient seems to be as he was, apart from his slight remaining pareses, he is painfully aware himself that this is not so.”

References

ResearchBlogging.org
Brodal A (1973). Self-observations and neuro-anatomical considerations after a stroke. Brain : a journal of neurology, 96 (4), 675-94 PMID: 4773860

Graziadio S, Tomasevic L, Assenza G, Tecchio F, & Eyre JA (2012). The myth of the ‘unaffected’ side after unilateral stroke: is reorganisation of the non-infarcted corticospinal system to re-establish balance the price for recovery? Experimental neurology, 238 (2), 168-75 PMID: 22981842

Professor Alf Brodal died in 1988, aged 78.

Image credit: Heidi Cartwright / Wellcome Images (top)
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