Ipsilesional and contralesional sensorimotor function after hemispherectomy: differences between distal and proximal function

Finger movement functions remain in the ipsilesional hemisphere and compensation by the contralesional hemisphere might not be expected after hemispherotomy -pre- and post-hemispherotomy evaluations in 8 cases

BACKGROUND

We hypothesized that fine finger motor functions are controlled by the ipsilesional hemisphere, and that gross motor functions are compensated for by the contralesional hemisphere after brain injury in humans. The purpose of this study was to compare finger movements before and after hemispherotomy that defunctionated the ipsilesional hemisphere for patients with hemispherical lesions.

METHODS

We statistically compared Brunnstrom stage of the fingers, arm (upper extremity), and leg (lower extremity) before and after hemispherotomy. Inclusion criteria for this study were: 1) hemispherotomy for hemispherical epilepsy; 2) a ≥ 6-month history of hemiparesis; 3) post-operative follow-up ≥ 6 months; 4) complete freedom from seizures without aura; and 5) application of our protocol for hemispherotomy.

RESULTS

Among 36 patients who underwent multi-lobe disconnection surgeries, 8 patients (2 girls, 6 boys) met the study criteria. Mean age at surgery was 6.38 years (range, 2-12 years; median, 6 years; standard deviation, 3.5 years). Paresis of the fingers was significantly exacerbated (p = 0.011) compared to pre-operatively, whereas that of the upper limbs (p = 0.07) and lower limbs (p = 0.103) was not.

CONCLUSION

Finger movement functions tend to remain in the ipsilesional hemisphere after brain injury, whereas gross motor movement functions such as those of the arms and legs are compensated for by the contralesional hemisphere in humans.

Cortex mapping of ipsilateral somatosensory area following anatomical hemispherectomy: a MEG study

A remarkable preservation of sensorimotor function is observed in patients with refractory epilepsy who were treated by hemispherectomy. Cortical regions in the remaining hemisphere or contralateral subcortical region contribute to the residual sensorimotor function. Somatosensory evoked field (SEF) is used to investigate the residual sensory function in hemispherectomized patients. The SEFs are usually recorded with magnetoencephalography (MEG). The objective is to investigate the ipsilateral cortical regions associated with residual sensory function in hemispherectomized patients using somatosensory evoked field techniques. Six patients with anatomical hemispherectomy were included. Ipsilateral and contralateral sensory functions were assessed by physical examination. Somatosensory evoked fields to electrical stimulation of the bilateral median nerves were recorded by MEG in the hemispherectomized patients and six control subjects. The stimulus intensity was adjusted to the minimum threshold that elicited a thumb twitch. The presumed neuronal source was identified as the equivalent current dipole. Six patients demonstrated different degrees of residual sensory function. Three patients had somatosensory evoked field activation in the ipsilateral cortex upon electrical stimulation of the hemiplegic hand. In these patients the locations of the ipsilateral sensorimotor cortex activation were in the primary somatosensory cortex (SI). The latency of the reliable somatosensory evoked field after stimulation of the median nerve was significantly longer for responses from the hemiplegic side compared with responses to stimulation of the median nerve from the normal side. In conclusion, ipsilateral sensory function has a time-locked relation to the cortical electromagnetic activation in the SI area of hemispherectomized patients.

fMRI and DTI assessment of patients undergoing radical epilepsy surgery

Hemispherectomy is effective for young patients suffered from unilateral cortical disease and severe drug-resistant epilepsy, but a major concern for hemispherectomy is the remaining brain functions and function recovery in patients after such surgery. In this study, seven patients were evaluated with clinical and imaging assessment pre- and post-surgery. Among them, four underwent anatomic hemispherectomy (AH) and three underwent subtotal hemispherectomy (functional hemispherectomy, FH). After the surgery, 71.4% (5/7) patients [(4/4) with AH and (1/3) with FH] became seizure free (Engel class I). Motor function of the paretic upper extremity unchanged in 4 patients and deteriorated in 3. Functional imaging results indicated that relocation of hand motor function (to the ipsilateral hemisphere) could take place before or after the surgery, or did not occur. Similar observations were made in the motor cortex activation on the paretic foot movement. In addition, both the affected and unaffected hemispheres underwent post-surgical changes in the corticospinal tracks (CST) in various degrees, but significant reinforcement of the CST in the remaining unaffected hemisphere was not evident. Further research is needed to reveal the true functional and structural changes of the remaining brain after surgery and to explore the mechanisms of such functional relocation and reorganization in patients underwent hemispherectomy.

Cerebral hemispherectomy: sensory scores before and after intensive mobility training

PURPOSE

It is unclear whether sensory modalities can be modified by rehabilitation and if sensory functions vary on the affected side many years after cerebral hemispherectomy. This pilot, proof-of-concept study assessed light touch and proprioception before and after 10 days of intensive mobility training in individuals after hemispherectomy.

METHODS

Light touch and proprioception of the upper and lower extremity was measured using the Fugl-Meyer sensory subtest on the paretic side in 18 individuals with hemispherectomy before and after mobility training. Sensory scores and differences related to mobility training were compared with clinical variables.

RESULTS

Patients were 7.1±5.7 years from time of surgery to sensory assessment and mobility training. Light touch scores were 81±22% and proprioception values were 64±23% of normal (p=0.0022). Light touch did not correlate with proprioception scores, and differences comparing after with before mobility training did not correlate. In multivariate analysis, younger age at seizure onset correlated with better light touch scores, and older age at onset correlated with improvements in light touch scores with mobility training. By comparison, proprioception scores were better in individuals with perinatal infarcts compared with Rasmussen encephalitis and Sturge-Weber. Post-training, proprioception scores were better in Sturge-Weber cases.

CONCLUSION

Light touch was less affected than proprioception on the paretic side after cerebral hemispherectomy. Improvements with mobility training correlated with older age at seizure onset and etiology. These findings suggest that many years after epilepsy surgery sensory functions are not static supporting the notion of existing developmental neuroplasticity of the remaining cerebral cortex along with brain stem and spinal cord pathways.

Speech and oral motor profile after childhood hemispherectomy

Hemispherectomy (disconnection or removal of an entire cerebral hemisphere) is a rare surgical procedure used for the relief of drug-resistant epilepsy in children. After hemispherectomy, contralateral hemiplegia persists whereas gross expressive and receptive language functions can be remarkably spared. Motor speech deficits have rarely been examined systematically, thus limiting the accuracy of postoperative prognosis. We describe the speech profiles of hemispherectomized participants characterizing their intelligibility, articulation, phonological speech errors, dysarthric features, and execution and sequencing of orofacial speech and non-speech movements. Thirteen participants who had undergone hemispherectomy (six left, seven right; nine with congenital, four with acquired hemiplegia; operated between four months and 13 years) were investigated. Results showed that all participants were intelligible but showed a mild dysarthric profile characterized by neuromuscular asymmetry and reduced quality and coordination of movements, features that are characteristic of adult-onset unilateral upper motor neuron dysarthria, flaccid-ataxic variant. In addition, one left and four right hemispherectomy cases presented with impaired production of speech and non-speech sequences. No participant showed evidence of verbal or oral dyspraxia. It is concluded that mild dysarthria is persistent after left or right hemispherectomy, irrespective of age at onset of hemiplegia. These results indicate incomplete functional re-organization for the control of fine speech motor movements throughout childhood, and provide no evidence of hemispheric differences.

Proximodistal gradient in the perception of delayed stiffness

Proximal and distal muscles are different in size, maximum force, mechanical action, and neuromuscular control. In the current study we explore the perception of delayed stiffness when probing is executed using movement of different joints. We found a proximodistal gradient in the amount of underestimation of delayed stiffness in the transition between probing with shoulder, elbow, and wrist joints. Moreover, there was a similar gradient in the optimal weighting between estimation of stiffness and the inverse of estimation of compliance that predicted the perception of the subjects. These gradients could not be ascribed to differences in movement amplitude, duration, velocity, and force amplitude because these variables were not significantly modulated by the joint used for probing. Mean force did not follow a similar gradient either. Therefore we suggest that the observed gradient in perception reveals a proximodistal gradient in control, such that proximal joints are dominated by force control, whereas distal joints are dominated by position control.

Sensorimotor function and sensorimotor tracts after hemispherectomy

Hemispherectomy is currently the only effective treatment for relieving constant seizures in children with severe or progressive unilateral cortical disease. Although early hemispherectomy has been advocated to avoid general dysfunction due to continued seizures, it remains unclear whether age at surgery affects specific sensorimotor functions. Little is know about the anatomical status of sensorimotor pathways after hemispherectomy and how it might relate to sensorimotor function. Here we measured motor function and sensory thresholds of the upper and lower limbs in 12 hemispherectomized patients. Diffusion tensor imaging (DTI) was used to determine status of brainstem corticospinal tracts and medial lemniscus. Hemispherectomy subjects showed remarkable recovery in both sensory and motor function. Many patients showed normal sensory vibration thresholds. Within the smaller Rasmussen's subgroup, we saw a relationship between age at surgery and sensorimotor function recovery (i.e. earlier was better). Anatomically, we found marked asymmetry in brainstem corticospinal tracts but preserved symmetry in the medial lemniscus, which may relate to robust sensory recovery. Age at surgery predicted anatomical status of brainstem sensorimotor tracts. In sum, we found that age at surgery influences anatomical changes in brainstem motor pathways, and may also relate to sensorimotor recovery patterns.

Motor and cognitive outcomes in children after functional hemispherectomy

PURPOSE

Medically intractable epilepsy is a chronic recurrence of seizures that often requires surgery to reduce or eliminate them. Although a reduction of seizures is the primary goal of hemispherectomy, the effect of surgery on motor and cognitive skills is also of importance. This review will provide a discussion of (1) evidence regarding motor and cognitive outcomes, (2) predictors of these outcomes, and (3) neural mechanisms responsible for preservation of function after hemispherectomy.

SUMMARY OF KEY POINTS

Motor and cognitive outcomes after hemispherectomy are variable and depend on many predictors including etiology and duration of seizure disorder, age at the time of surgery, premorbid status, and postsurgical seizure control. A refined ipsilateral pathway may explain the preservation of motor function in some children.

CONCLUSIONS

A clear understanding of outcome predictors is important for planning effective rehabilitative programs after surgery.