Motor Organization in Schizencephaly: Outcomes of Transcranial Magnetic Stimulation and Diffusion Tensor Imaging of Motor Tract Projections Correlate with the Different Domains of Hand Function.

OBJECTIVE: Schizencephaly is a rare congenital malformation that causes motor impairment. To determine the treatment strategy, each domain of the motor functions should be appropriately evaluated. We correlated a color map of diffusion tensor imaging (DTI) and transcranial magnetic stimulation (TMS) with the hand function test (HFT) to identify the type of hand function that each test (DTI and TMS) reflects. Further, we attempted to demonstrate the motor neuron organization in schizencephaly. METHOD: This retrospective study was conducted on 12 patients with schizencephaly. TMS was conducted in the first dorsal interosseous (FDI), biceps (BB), and deltoid muscles of the upper extremity, and contralateral MEP (cMEP) and ipsilateral MEP (iMEP) were recorded. The HFT included the grip strength, box and block (B&B), and 9-hole peg test. The schizencephalic cleft was confirmed using magnetic resonance imaging, and the corticospinal tract (CST) was identified using the color map of DTI. The symmetry indices for the peduncle and CST at pons level were calculated as the ratios of the cross-sectional area of the less-affected side and that of the more-affected side. RESULT: In the more-affected hemisphere TMS, no iMEP was obtained. In the less-affected hemisphere TMS, the iMEP response was detected in 9 patients and cMEP in all patients, which was similar to the pattern observed in unilateral lesion. Paretic hand grip strength was strongly correlated with the presence of iMEP (p = 0.044). The symmetry index of the color map of DTI was significantly correlated with the B&B (p = 0.008, R 2 = 0.416), whereas the symmetry index of the peduncle was not correlated with all HFTs. CONCLUSION: In patients with schizencephaly, the iMEP response rate is correlated with the hand function related to strength, while the symmetricity of the CST by the color map of DTI is correlated with the hand function associated with dexterity. Additionally, we suggest the possible motor organization pattern of schizencephaly following interhemispheric competition.

The lateral cerebral peduncle approach to ventrally placed intra-axial midbrain tumors: A technical note.

We describe the anatomical landmarks and surgical feasibility of a novel 'safe' brainstem entry zone to approach ventrally placed intra-axial midbrain tumors. The anatomy of the brainstem was specifically studied to evaluate safe surgical entry zone in the midbrain on two formalin fixed silicon injected cadaver head specimens. A novel entry point through the lateral one - fifth of the cerebral peduncle was identified to be 'safe' to approach lesions of the ventral midbrain. Three patients, having oculomotor schwannoma, peduncular glioma and a peduncular cavernoma were operated using this safe entry zone. To approach the midbrain, retrosigmoid lateral supracerebellar route was used in two patients and a basal subtemporal avenue was deployed in one patient. On the basis of fine microanatomical dissection on cadavers, a novel entry point through the lateral one-fifth of the cerebral peduncle, 5 mm anterior to the lateral mesencephalic sulcus and approximately 5 mm superior to the fourth nerve was identified. The proposed brainstem entry point traverses the parieto-temporo-occipital pontine fibers and the trajectory is between the corticospinal tracts ventrally and the substantia nigra dorsally. Three patients were operated successfully using the approach. There were no post-operative motor, sensory or extra-pyramidal deficits. The corridor through the lateral one-fifth of the cerebral peduncle presents a safe and relative 'easy' surgical route to approach ventrally placed intra-axial midbrain tumors.

An Eyebrow, Supracarotid Triangle Approach for Lesions at the Ventral Thalamopeduncular Junction: A Technical Report.

BACKGROUND: Lesions arising at the ventral thalamopeduncular junction are difficult to resect. In addition to being relatively inaccessible, these lesions are located in one of the most sensitive areas of the brain. A critical question is whether new approaches could be developed to allow surgeons to adequately resect these lesions with reasonable outcomes. In the present report, we describe our approach to resect lesions in this region of the brain using an eyebrow craniotomy approach with a trajectory through the supracarotid triangle. METHODS: Through retrospective data collection, we present a small series of patients who had undergone an eyebrow, supracarotid triangle approach to resect lesions located at the thalamopeduncular junction. We describe our surgical technique and report patient outcomes using this approach. RESULTS: Three patients had undergone an eyebrow, supracarotid approach for resection of a lesion arising at the ventral thalamopeduncular junction. Two patients had presented with a cavernoma and one with a pilocytic astrocytoma. Complete resection of all 3 lesions was achieved during surgery without any intraoperative complications. No patient developed permanent contralateral weakness despite entering the peduncle during surgery. One patient developed permanent paresthesia in his left hand. CONCLUSIONS: Lesions arising at the ventral thalamopeduncular junction can be adequately resected with reasonable outcomes using an eyebrow, supracarotid triangle approach. This operative technique establishes another potential operative corridor by which neurosurgeons can resect lesions arising within this relatively inaccessible part of the brain.

Holmes Tremor due to Artery of Percheron Infarct: Clinical Case and Treatment Using Deep Brain Stimulation of the Vim and ZI Targets.

Background: Holmes tremor (HT) arises from disruption of the cerebellothalamocortical pathways. A lesion can interrupt the projection at any point, resulting in this tremor. We describe a case of HT due to the rare artery of Percheron infarct and its successful treatment using deep brain stimulation. Case report: A 62-year-old woman with a right medial cerebral peduncle and bilateral thalamic stroke developed HT. Ventral intermediate nucleus (Vim) zona incerta (ZI) deep brain stimulation (DBS) surgery was performed, with improvement in her tremor. Discussion: Our case supports the theory that the more caudal ZI target in combination with Vim is beneficial in treating poorly DBS-responsive tremors such as HT.

Cerebral Peduncle Volume and Motor Function Following Adult Hemispherectomy.

BACKGROUND: Hemispherectomy is a successful and well-described treatment option for pediatric patients with hemispheric ictal onset, but adult outcomes have been far less studied. We describe the outcomes in adult patients with medically refractory epilepsy and hemispheric disease and the relationship to cerebral peduncle volume. CASE DESCRIPTIONS: We retrospectively reviewed adult hemispherectomy patients at our institution from 2015 to 2018. Patient data including demographic information, pathologic changes, seizure-free outcomes, and ipsilateral (i.e., surgical side) and contralateral (i.e., functional side) cerebral peduncle volume data were collected. We identified 4 adult patients who underwent hemispherectomy. The mean age at surgery was roughly 25 years. All patients were categorized as Engel I or II, and motor scores at last follow-up were unchanged. The mean volume for contralateral and ipsilateral cerebral peduncle means were 1.42 and 0.78 cm3, respectively (P = 0.01). CONCLUSIONS: These findings suggest that smaller ipsilateral cerebral peduncle size could potentially be associated with unchanged postoperative hemiparesis. We hypothesize that smaller ipsilateral peduncle size could have represented corticospinal tract reorganization in childhood, implying that the removed brain matter was mostly noncontributory to contralateral motor function.

[Symmetrical lesions of the cerebral peduncles and internal capsules on MRI in a patient with extranodal NK/T cell lymphoma].

A 72-year-old man was admitted to our hospital because of subacute progressive consciousness disturbance. FLAIR images showed diffuse high intensity areas in the bilateral thalamus, basal ganglia, and white matter. Chest CT revealed a mass in the right lung. The patient was diagnosed with extranodal natural killer/T cell lymphoma (ENKL) according to the results of a biopsy of the right pulmonary mass. The FLAIR images showed diffuse white matter lesions, without a mass such as lymphomatosis cerebri. On diffusion-weighted images, symmetrical high-intensity lesions of the cerebral peduncle and the internal capsule suggested high-density lymphoma cells around neurons. ENKL of the central nervous system and lung is a very rare neoplasm, and this case showed characteristic images.

Tractography guides the approach for resection of thalamopeduncular tumors.

BACKGROUND: Thalamopeduncular tumors arise at the junction of the inferior thalamus and cerebral peduncle, and present with a common clinical syndrome of progressive spastic hemiparesis. METHOD: Formal preoperative magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were performed. Postoperative MRI was obtained to evaluate the extent of tumor resection. A prospective analysis of clinical outcomes was then conducted by the senior author. CONCLUSIONS: Preoperative tractography is a useful adjunct to surgical planning in tumors that displace motor pathways. Gross total resection of pilocytic astrocytomas usually results in cure, and therefore should be entertained when developing treatment strategies for thalamopeduncular tumors of childhood.