Abstracts & Commentary
Sources: Schindler F, et al. Neck muscle vibration induces lasting recovery in spatial neglect. J Neurol Neurosurg Psychiatry. 2002;73:412-419; Robertson IH. Editorial commentary: Brain rehabilitation. Cognitive neuroscience and brain rehabilitation: A promise kept. J Neurol Neurosurg Psychiatry. 2002;73:357.
An impaired response to contralateral space following right cerebral stroke causes patients to behave as if the left half of the world did not exist, which limits their potential to benefit from standard rehabilitation techniques. Therefore, to reduce neglect symptoms, various alternative techniques have been used including: attention training,1 vestibular stimulation,2 neck muscle vibration,3 prism adaptation,4 as well as others.
Schindler and colleagues in Munich evaluated whether visual exploration training alone or in combination with electromechanical vibration of the left neck muscles of patients while they engaged in visual search exercises were effective techniques for the rehabilitation of spatial neglect. They studied 2 matched groups each of 10 right-handed ischemic stroke patients with moderate-to-severe left hemiparesis and persistent neglect. After a baseline of 3 weeks to allow for spontaneous recovery, half of the patients received 15 sessions of visual exploration training. In the second phase, this treatment was combined with neck muscle vibration. The other half of the treatment group received the treatment in reverse order.
The effects of treatment were assessed with respect to different aspects of the neglect disorder, such as impaired perception of the body’s normal coordinate frame of reference exploration deficits in visual and tactile modes and visual size distortion. The transfer of treatment effects of activities of daily living was tested by reading a questionnaire. Variables were measured at baseline, post-treatment, and after 2 months.
Combination treatment produced a marked and lasting reduction in visual neglect that transferred to the tactile mode and thus had practical benefits in real life. Schindler et al explained the positive results of neck muscle vibration on visual and tactile exploration in patients with neglect in terms of an effect on the "egocentric reference system for spatio-motor transformation by generating a corrective head-on-trunk signal."
Schindler et al compare the effect of their contralesional electromechanical neck muscle stimulation with standard contralesional caloric vestibular canal stimulation. Remember the mnemonic for the direction of caloric-induced nystagmus, COWS: Cold Opposite-Warm Same. Neck muscle stimulation seems easier to perform than warm water irrigation of the left external auditory canal and doesn’t induce vertigo or vomiting.
As pointed out by Robertson in his editorial, Schindler et al have done something implausible: applied a vibrator temporarily combined with 15 treatment sessions over 3 weeks and obtained lasting results in a condition considered by many to be untreatable. If the results are validated by other groups, then Schindler et al will have made a significant contribution to the well being and recovery of stroke patients. —John J. Caronna
Dr. Caronna, Vice-Chairman, Department of Neurology, Cornell University Medical Center; Professor of Clinical Neurology, New York Hospital, is Associate Editor of Neurology Alert.
1. Robertson IH, et al. J Clin Exp Neuropsychol. 1995;17:416-430.
2. Rubens AB. Neurology. 1985;35:1019-1024.
3. Karnath HO, Christ K, Hartje W. Brain. 1993;116:383-396.
4. Frassinetti F, et al. Brain. 2002;125:608-623.