Nowak D A, Rosenkranz K, Topka H, Rothwell J
Sobell Department of Motor Neuroscience and Movements Disorders, Institute of Neurology, University of London, UK.
J Neurol Neurosurg Psychiatry. 2005 Jul;76(7):953-9. doi: 10.1136/jnnp.2004.043943.
Focal task specific dystonia occurs preferentially during performance of a specific task. There may be an inefficiently high grip force when doing manipulative tasks other than the trigger task, possibly reflecting a generalised impairment of sensory-motor integration.
To examine how well subjects with writer's cramp (n = 4) or musician's cramp (n = 5) adapted their grip force when lifting a new object or catching a weight.
Nine patients with focal hand dystonia and 10 controls were studied. Experiments addressed different motor behaviours: (A) lifting and holding an object; (B) adjusting grip force in anticipation of or in reaction to a change in load force by catching a small weight dropped expectedly or unexpectedly into a hand held receptacle.
In (A), patients produced a grip force overshoot during the initial lifts; force overflow was most pronounced in those with writer's cramp. Patients and controls adjusted their grip force to object weight within one or two lifts, though patients settled to a steady force level above normal. In (B), patients with focal hand dystonia and normal controls showed similar predictive grip force adjustments to expected changes in object load, suggesting that this aspect of sensory-motor integration was normal. Patients had a shorter latency of grip force response than controls after an unexpected load increase, reflecting either a greater level of preparatory motor activity or a disinhibited spinal reflex response.
The overall increased grip force in patients with focal hand dystonia is likely to be a prelearned phenomenon rather than a primary disorder of sensory-motor integration.
局灶性任务特异性肌张力障碍在特定任务执行过程中更易出现。在进行触发任务以外的操作任务时，可能存在抓握力过高且效率低下的情况，这可能反映了感觉运动整合的普遍受损。
研究书写痉挛患者（n = 4）或音乐家痉挛患者（n = 5）在拿起新物体或接住重物时抓握力的适应情况。
对9例局灶性手部肌张力障碍患者和10名对照者进行研究。实验涉及不同的运动行为：（A）拿起并握住物体；（B）通过接住预期或意外落入手持容器中的小重物，预期或应对负载力变化时调整抓握力。
在（A）中，患者在最初拿起物体时产生抓握力过冲；书写痉挛患者的力溢出最为明显。患者和对照者在一两次拿起物体的过程中就将抓握力调整至与物体重量相适应，不过患者最终稳定在高于正常水平的稳定力值。在（B）中，局灶性手部肌张力障碍患者和正常对照者对物体负载的预期变化表现出相似的预测性抓握力调整，表明感觉运动整合的这一方面是正常的。在意外负载增加后，患者抓握力反应的潜伏期比对照者短，这反映出其准备性运动活动水平更高或脊髓反射反应抑制解除。
局灶性手部肌张力障碍患者抓握力总体增加可能是一种预先习得的现象，而非感觉运动整合的原发性障碍。
