Functional brain imaging, clinical and neurophysiological outcome of visual rehabilitation in a chronic stroke patient

PURPOSE

To study rehabilitation outcome in a chronic visual field defect patient using positron emission tomography (PET) imaging, clinical, and neurophysiological measures.

METHODS

A patient with chronic visual field defect was rehabilitated using a computer program over a three-month period. Evaluations of rehabilitation effects were done before and after training, and after a three-month follow-up with perimetry, visual evoked potentials (VEP), subjective questionnaire, and PET activation studies of regional cerebral blood flow (rCBF).

RESULTS

In perimetry, the visual field increased during the training, and the patient also experienced subjective improvement. In VEP, a previously absent P100 component was identified after the training. In PET, increases in rCBF were diffuse immediately after the training, and more occipital after the late follow-up. A significant positive correlation between the increase in rCBF and improvement in clinical measures was found in the lingual gyrus in the contralesional hemisphere.

CONCLUSIONS

All clinical measures showed improvement after rehabilitation, and this was maintained during the follow-up. In PET, a more generalized effect, found at the beginning, later concentrated in the occipital cortex. The results suggest that visual training may cause plastic changes in the brain, and that these changes can be detected both with clinical measures and with functional imaging.

Recovery of somatosensory deficits in acute stroke

OBJECTIVES

To study the recovery of somatosensory deficits after acute stroke.

MATERIAL AND METHODS

A detailed clinical examination of sensation, median nerve somatosensory evoked potentials (SEP), quantitative sensory tests (QST), and subjective evaluation were performed in five acute stroke patients at three control time points up to 12 months after the stroke.

RESULTS

The deficit recovered at least partially in all patients, mostly within 3 months after stroke. The improvement in warm and vibration detection thresholds occurred between 3 and 12 months. The SEP improved both by 3 and 12 months.

CONCLUSION

The recovery of subjective sensory disturbance occurred in line with the improvement of the clinical sensory tests and QST. The most sensitive measure for somatosensory dysfunction at the early phase was graphesthesia. In our patients, initially normal SEP with a sensory deficit resulted in excellent clinical recovery, whereas initially absent SEP did not necessarily predict poor outcome.

Effects of a 902 MHz mobile phone on cerebral blood flow in humans: a PET study

Fourteen healthy right-handed subjects were scanned using PET with a [15O]water tracer during exposure to electromagnetic field (EMF) emitted by a mobile phone and a sham-exposure under double-blind conditions. During scanning, the subjects performed a visual working memory task. Exposure to an active mobile phone produced a relative decrease in regional cerebral blood flow (rCBF) bilaterally in the auditory cortex but no rCBF changes were observed in the area of maximum EMF. It is possible that these remote findings were caused by the EMF emitted by the active mobile phone. A more likely interpretation of the present findings were a result of an auditory signal from the active mobile phone. Therefore, it is not reasoned to attribute this finding to the EMF emitted by the phone. Further study on human rCBF during exposure to EMF of a mobile phone is needed.

Rehabilitation of chronic post-stroke visual field defect with computer-assisted training: a clinical and neurophysiological study

PURPOSE

Our aim was to study whether homonymous visual field defects could be restored in chronic stroke patients (N = 5) using computer-assisted training, and whether the possible beneficial effect could be maintained. Visual evoked potential (VEP) recordings were applied to evaluate whether they could demonstrate the possible training effects at the cortical level.

METHODS

We applied a specially designed computer program in the training. Subjective assessment, static and kinetic perimetry, and pattern reversal hemifield VEP recordings were used to detect the possible changes.

RESULTS

Two patients showed improvements immediately after the training in static perimetry. Further improvements were detected at a later follow-up in three patients. With kinetic perimetry, improvements were detected in three patients. The visual field defect was detected with VEP recordings in four patients before the training, and improvements could be verified with the method in three patients, two of which clearly improved in the static perimetry as well.

CONCLUSIONS

In three patients, the visual defect diminished with the computer-assisted method. It seems evident that visual field defects resulting from stroke can be partially restored even in the chronic phase.