Impaired force control in writer's cramp showing a bilateral deficit in sensorimotor integration.

BACKGROUND: Abnormal cortical processing of sensory inputs has been found bilaterally in writer's cramp (WC). This study tested the hypothesis that patients with WC have an impaired ability to adjust grip forces according to visual and somatosensory cues in both hands. METHODS: A unimanual visuomotor force-tracking task and a bimanual sense of effort force-matching task were performed by WC patients and healthy controls. RESULTS: In visuomotor tracking, WC patients showed increased error, greater variability, and longer release duration than controls. In the force-matching task, patients underestimated, whereas controls overestimated, the force applied in the other hand. Visuomotor tracking and force matching were equally impaired in both the symptomatic and nonsymptomatic hand in WC patients. CONCLUSIONS: This study provides evidence of bilaterally impaired grip-force control in WC, when using visual or sense of effort cues. This suggests a generalized subclinical deficit in sensorimotor integration in WC.

Combination of anodal tDCS of the cerebellum with a goal-oriented motor training to treat cervical dystonia: a pilot case series.

Background: Transcranial Direct Current Stimulation (tDCS) of the cerebellum shows promise for the treatment of dystonia. Specific motor rehabilitation programs have also been developed in this context. However, the combination of these two approaches has not yet been evaluated to determine their therapeutic potential. Methods: We report a series of 5 patients with cervical dystonia (CD) poorly controlled by botulinum toxin injections. They were initially treated by a protocol of repeated daily sessions (for 3 or 5 days) of cerebellar anodal tDCS (cer-atDCS) applied alone. In a second time, additional protocols of cer-atDCS were performed in combination with a program of goal-oriented motor training exercises (Mot-Training), specifically developed for the treatment of CD. The clinical impact of the procedures was assessed on the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Results: Compared to baseline, the maximum percentage of TWSTRS total score improvement was 37% on average after cer-atDCS performed alone (p = 0.147, not significant) and 53% on average after cer-atDCS combined with Mot-Training (p = 0.014, significant). The TWSTRS pain and functional handicap subscores also improved after the combined protocol. A score of (+3) to (+5) was rated on the TWSTRS response scale after cer-atDCS performed alone or the combined protocol, corresponding to a moderate to striking improvement on dystonia and pain. This improvement lasted longer after the combined protocol than after cer-atDCS alone (3.4 vs. 1.4 months on average, p = 0.011). Conclusion: The combination of cer-atDCS with Mot-Training produced a greater and more prolonged improvement than the application of cer-atDCS alone. Such a combined therapeutic procedure is easy to perform and opens important perspectives in the long-term treatment of CD. These results remain to be confirmed by a randomized sham-controlled trial on a larger sample.

Assessment of axial rotation movement in cervical dystonia using cone-beam computed tomography.

BACKGROUND: Cervical dystonia is a neurological disorder characterized by involuntary muscle contractions and abnormal postures of the head and neck. Botulinum neurotoxin injection is the first-line treatment. Imaging determination of the cervical segments involved (lower or upper according to the torticollis-torticaput [COL-CAP] Classification) is an aid in determining the muscles to be injected. We aimed to clarify the impact of dystonia on posture and rotational movement of cervical vertebrae in the transverse plane. METHODS: A comparative study was conducted in a movement disorders department. Ten people with cervical dystonia and 10 matched healthy subjects (without cervical dystonia) were recruited. 3-D images of posture and cervical range of motion in axial rotation in the sitting position were recorded by using a cone-beam CT scanner. Range of rotational motion of the upper cervical spine from the occipital bone to fourth cervical vertebra was measured and compared between the two groups. FINDINGS: The head posture analysis showed that the total cervical spine position was more significantly distant from the neutral position for people with dystonia than healthy subjects (p = 0.007). The rotational range of motion of the cervical spine was significantly lower in cervical dystonia participants than in healthy subjects for the total (p = 0.026) and for upper cervical spine (p = 0.004). INTERPRETATION: We demonstrated, by means of cone-beam CT, that the disorganization of movements due to cervical dystonia affected the upper cervical spine and mostly the atlantoaxial joint. The involvement of rotator muscles at this cervical level should be considered more in treatments.

Somatosensory cortical remodelling after rehabilitation and clinical benefit of in writer's cramp.

In order to explore the pathophysiological basis of a new rehabilitation therapy in writer's cramp (WC), healthy controls, untreated WC patients and WC patients who recovered a legible handwriting after rehabilitation were explored using magnetoencephalography, and the somatosensory evoked fields of fingers I, II, III and V in the sensory cortex were studied. In the cortex controlling the dystonic limb, the size of the hand representation in the trained patients was similar to that of healthy controls, and significantly different from that of untrained patients. Trained patients exhibited 'super-normal' reorganisation of the finger maps. In the cortex controlling the non-dystonic limb, there was little difference between trained and untrained patients, and the hand representation was enlarged and disorganised. The authors hypothesise that prolonged tailored rehabilitation in WC may induce long-term plasticity phenomena, lateralised to the cortex controlling the dystonic hand.

Time-frequency analysis reveals decreased high-frequency oscillations in writer's cramp.

High-frequency oscillations (HFO) have been suggested to reflect the activity of thalamocortical and/or intracortical neurons bursting at high frequencies. These circuits seem to be involved in pathophysiological mechanisms of focal dystonia. In healthy subjects, we characterized the spectrotemporal properties of HFO patterns evoked by dominant-hand median-nerve stimulation, using magnetoencephalography coupled with time-frequency analysis. Then, we investigated HFO in patients with writer's cramp and found that HFO patterns are strongly decreased in power and disorganized in time. This supports the assumption that abnormal HFOs reflect pathophysiological mechanisms occurring in focal dystonia, possibly resulting from a dysfunction of somatosensory processing.

Manual Dexterity in Schizophrenia-A Neglected Clinical Marker?

Impaired manual dexterity is commonly observed in schizophrenia. However, a quantitative description of key sensorimotor components contributing to impaired dexterity is lacking. Whether the key components of dexterity are differentially affected and how they relate to clinical characteristics also remains unclear. We quantified the degree of dexterity in 35 stabilized patients with schizophrenia and in 20 age-matched control subjects using four visuomotor tasks: (i) force tracking to quantify visuomotor precision, (ii) sequential finger tapping to measure motor sequence recall, (iii) single-finger tapping to assess temporal regularity, and (iv) multi-finger tapping to measure independence of finger movements. Diverse clinical and neuropsychological tests were also applied. A patient subgroup (N = 15) participated in a 14-week cognitive remediation protocol and was assessed before and after remediation. Compared to control subjects, patients with schizophrenia showed greater error in force tracking, poorer recall of tapping sequences, decreased tapping regularity, and reduced degree of finger individuation. A composite performance measure discriminated patients from controls with sensitivity = 0.79 and specificity = 0.9. Aside from force-tracking error, no other dexterity components correlated with antipsychotic medication. In patients, some dexterity components correlated with neurological soft signs, Positive and Negative Syndrome Scale (PANSS), or neuropsychological scores. This suggests differential cognitive contributions to these components. Cognitive remediation lead to significant improvement in PANSS, tracking error, and sequence recall (without change in medication). These findings show that multiple aspects of sensorimotor control contribute to impaired manual dexterity in schizophrenia. Only visuomotor precision was related to antipsychotic medication. Good diagnostic accuracy and responsiveness to treatment suggest that manual dexterity may represent a useful clinical marker in schizophrenia.

Does dystonic muscle activity affect sense of effort in cervical dystonia?

BACKGROUND: Focal dystonia has been associated with deficient processing of sense of effort cues. However, corresponding studies are lacking in cervical dystonia (CD). We hypothesized that dystonic muscle activity would perturb neck force control based on sense of effort cues. METHODS: Neck extension force control was investigated in 18 CD patients with different clinical features (7 with and 11 without retrocollis) and in 19 control subjects. Subjects performed force-matching and force-maintaining tasks at 5% and 20% of maximum voluntary contraction (MVC). Three task conditions were tested: i) with visual force feedback, ii) without visual feedback (requiring use of sense of effort), iii) without visual feedback, but with neck extensor muscle vibration (modifying muscle afferent cues). Trapezius muscle activity was recorded using electromyography (EMG). RESULTS: CD patients did not differ in task performance from healthy subjects when using visual feedback (ANOVA, p>0.7). In contrast, when relying on sense of effort cues (without visual feedback, 5% MVC), force control was impaired in patients without retrocollis (p = 0.006), but not in patients with retrocollis (p>0.2). Compared to controls, muscle vibration without visual feedback significantly affected performance in patients with retrocollis (p<0.001), but not in patients without retrocollis. Extensor EMG during rest, included as covariate in ANOVA, explained these group differences. CONCLUSION: This study shows that muscle afferent feedback biases sense of effort cues when controlling neck forces in patients with CD. The bias acts on peripheral or central sense of effort cues depending on whether the task involves dystonic muscles. This may explain why patients with retrocollis more accurately matched isometric neck extension forces. This highlights the need to consider clinical features (pattern of dystonic muscles) when evaluating sensorimotor integration in CD.

Upper Limb Outcome Measures Used in Stroke Rehabilitation Studies: A Systematic Literature Review.

BACKGROUND: Establishing which upper limb outcome measures are most commonly used in stroke studies may help in improving consensus among scientists and clinicians. OBJECTIVE: In this study we aimed to identify the most commonly used upper limb outcome measures in intervention studies after stroke and to describe domains covered according to ICF, how measures are combined, and how their use varies geographically and over time. METHODS: Pubmed, CinHAL, and PeDRO databases were searched for upper limb intervention studies in stroke according to PRISMA guidelines and477 studies were included. RESULTS: In studies 48different outcome measures were found. Only 15 of these outcome measures were used in more than 5% of the studies. The Fugl-Meyer Test (FMT)was the most commonly used measure (in 36% of studies). Commonly used measures covered ICF domains of body function and activity to varying extents. Most studies (72%) combined multiple outcome measures: the FMT was often combined with the Motor Activity Log (MAL), the Wolf Motor Function Test and the Action Research Arm Test, but infrequently combined with the Motor Assessment Scale or the Nine Hole Peg Test. Key components of manual dexterity such as selective finger movements were rarely measured. Frequency of use increased over a twelve-year period for the FMT and for assessments of kinematics, whereas other measures, such as the MAL and the Jebsen Taylor Hand Test showed decreased use over time. Use varied largely between countries showing low international consensus. CONCLUSIONS: The results showed a large diversity of outcome measures used across studies. However, a growing number of studies used the FMT, a neurological test with good psychometric properties. For thorough assessment the FMT needs to be combined with functional measures. These findings illustrate the need for strategies to build international consensus on appropriate outcome measures for upper limb function after stroke.

Baseline Features Influencing the Effectiveness of Retraining Therapy for Writer's Cramp.

Background: The effectiveness of retraining therapy (RT) for writer's cramp is difficult to predict and its determinants are unknown. Methods: We examined factors potentially predicting improved legibility after RT in patients with writer's cramp (WC). We reviewed the files of 693 WC patients treated with RT from 1995 to 2009. Standardized assessments were made both at baseline and after 2 months of RT in 305 patients. The effect of RT on legibility was evaluated by using the handwriting subscore of the Burke-Fahn-Marsden (BFM) disability scale. Initial and final handwriting samples were blindly scored in random order. Associations between WC patterns and changes in legibility were identified by uni- and multivariable analyses. Results: Legibility improved by ≥1 point in the BFM handwriting subscore in 93 patients (31%). WC patients who improved were more likely to have synergic dystonic patterns involving the wrist and forearm (60% vs. 40%; P = 0.03) and less likely to have flexion of fingers F3 to F5 (19% vs. 81%; P = 0.017). Outcome was not related to gender, age, or dystonia duration. Our results confirm that retraining therapy could improve legibility in patients with writer's cramp. Conclusions: The pattern of writer's cramp can help to identify patients who are most likely to benefit from retraining therapy, regardless of age, gender, and disease duration.