Sumito Sato

Primary germinoma arising from the midbrain.

SummaryA 29-year-old man presented with diplopia, dysarthria, anisocoria, oculomotor nerve paralysis, abducens nerve paralysis, right facial palsy, and spastic hemiparetic gait. Magnetic resonance imaging (MRI) showed a homogenously enhanced mass in the midbrain. MRI-guided stereotactic biopsy was performed, and the histologic diagnosis was pure germinoma. The tumor disappeared after chemotherapy and radiotherapy. Germinoma should be included in the differential diagnosis of midbrain lesions in young adults. MRI-guided stereotactic biopsy provided a helpful diagnostic clue in a patient with a midbrain lesion.

Sinus thrombosis probably resulting from a dural arteriovenous fistula development in the superior sagittal sinus.

A 59-year-old woman developed speech difficulties and was referred to our hospital the next day. She was conscious but showed speech arrest. Physical examination did not show a neurological abnormality or signs of raised intracranial pressure. Laboratory findings, including data for coagulability, were normal. Computed tomography showed a small subcortical haematoma in the left frontal lobe. Angiography of the left internal carotid did not show a source for haemorrhage but showed poor filling in the frontal area and a filling defect of anterior portion of the superior sagittal sinus (SSS) (Fig. i.a). Angiography of the external carotid showed a dural arteriovenous fistula (DAVF) in the SSS fed by middle meningeal arteries (MMAs) on both sides and draining into the SSS through the left frontal deep medullary and cortical veins (Fig. 1.b). Magnetic resonance imaging (MRI). showed a thrombus in the SSS corresponding to the filling defect seen on angiography. It was inhomogeneous on Tl and hyperintense on T2 weighted imaging (Fig. 1.c, d). A craniotomy was done. We interrupted the feeding MMAs, and widely removed and cauterized the dura near the DAVF, in order to prevent growth of collateral feeding pathways. The symptoms gradually subsided. Angiography was repeated 12 days after the surgery and showed disappearance of the DAVF and improvement of venous return in the left frontal region. She was discharged without deficit. MRI three months later showed persistence of the sinus thrombosis, hypo-intense on both T1 and T2 weighted imaging. She has been followed up uneventfully, for one year.

The Appropriate Surgical Approach to a Greater Petrosal Nerve Schwannoma in the Setting of Temporal Lobe Edema

BACKGROUND Facial nerve schwannomas are rare lesions that constitute only 0.8% of all intrapetrous mass lesions. The least frequent lesions are tumors originating in the greater petrosal nerve (GPN). We present a case of a GPN schwannoma with temporal lobe edema in which the patient was operated on using an extradural and intradural approach to prevent complications. CASE DESCRIPTION A 66-year-old woman with vertigo and abnormal magnetic resonance imaging findings was referred to our department. Computed tomography scan revealed an isodense subtemporal mass with partial rim calcification and petrosal bone apex erosion. Magnetic resonance imaging confirmed a 22-mm left middle fossa lesion with heterogeneous enhancement and edema of the temporal lobe. A left temporal craniotomy to the middle fossa was performed. The initial extradural exploration revealed the tumor to be in the Glasscock triangle, mainly involving the location of the GPN. The tumor was removed through an intradural approach in piecemeal fashion. Finally, using an extradural and intradural middle fossa approach, the tumor was totally removed, leaving the capsule on the middle fossa floor with continuous facial nerve monitoring. The postoperative course was uneventful without complications of xerophthalmia and facial palsy. CONCLUSIONS GPN schwannomas are very rare lesions. The extradural and intradural middle fossa approach was used to preserve the tumor capsule around the GPN. Using this technique, one can safely protect the geniculate ganglion and the GPN.

Safe Stereotactic Biopsy for Basal Ganglia Lesions: Avoiding Injury to the Basal Perforating Arteries

Background: One of the most serious complications of stereotactic biopsy is postoperative symptomatic hemorrhage due to injury to the basal perforating arteries such as the lenticulostriate arteries neighboring the basal ganglia lesions. Objectives: A new target-planning method was proposed to reduce hemorrhagic complications by avoiding injury to the perforating arteries. Methods: Three-dimensional 3-T time-of-flight (3D 3-T TOF) imaging was applied to delineate the basal perforating arteries such as the lenticulostriate arteries. The incidence of postoperative hemorrhage in basal ganglia cases was compared between a new method using 3D 3-T TOF and a conventional target-planning method based on contrast-enhanced T1-weighted magnetic resonance images obtained by 1.5-T scanning. Results: 3D 3-T TOF imaging could delineate the basal perforating arteries sufficiently in target planning. No postoperative hemorrhage occurred with the new method (n = 10), while 6 postoperative hemorrhages occurred with the conventional method (n = 14). The new method significantly reduced the occurrence of postoperative hemorrhages (p = 0.017). Conclusions: 3D 3-T TOF MR imaging with contrast medium administration provides useful information about the perforating arteries and allows safe stereotactic biopsy of basal ganglia lesions.

Intraoperative Visualization of Subependymal Arteries at the Atrium Supplying the Descending Motor Pathway

OBJECTIVE We previously disclosed that damage to the subependymal arteries (SEAs) caused by coagulation of the choroid plexus at the atrium can result in infarction within the lateral posterior choroidal artery territory, followed by hemiparesis. The present study describes the intraoperative anatomical findings of the SEAs and choroid plexus at the atrium, which were verified only by a few cadaveric studies. METHODS Locations of the SEA and descending motor pathway were determined with the neuronavigation system and subcortical electrical stimulation in 8 cases of periatrial brain tumor. Indocyanine green videoangiography was performed to verify the blood flow in the choroid plexus and SEAs. RESULTS Intraoperative visualization of the SEAs was performed successfully in all patients. The neuronavigation system and subcortical electrical stimulation mapping demonstrated that these SEAs penetrated into the descending motor pathway. Indocyanine green depicted the blood flow of the SEAs entering the wall of the lateral ventricle and adjacent brain parenchyma. The blood flow directions between the SEAs and choroid plexus were not uniform, because the SEAs were filled ahead of the choroid plexus in 3 cases, whereas the choroid plexus was filled first in the other 2 cases. CONCLUSIONS Manipulations to the inner side of the choroid plexus at the transition from the atrium to the body of lateral ventricle can damage the SEAs. Not only coagulation of the SEAs themselves, but also coagulation of choroid plexus itself may reduce the blood flow in the SEAs, resulting in ischemic complications at descending motor pathway.

Deep Pain Loss in Syringomyelia and Other Spinal Cord Lesions

Deep pain is an important muscle nociception; however, testing for it has long been ignored in the clinical field. The authors studied the clinical significance of testing deep pain sensation in patients with spinal cord lesions. Deep pain sensations evoked by squeezing superficial muscles were examined in 19 patients with syringomyelia, 50 with cervical spondylosis, 2 with Hirayama disease, and 2 patients with spinal neurinoma. Deep pain sensitivity was graded as hyper-, normal, hypo-, and loss compared to that of the trapezius muscle in the intact side and was compared with other neurological findings. In those patients with syringomyelia, deep pain was diminished or lost in 14 (74%) patients. Only 24% of the patients with cervical spondylosis presented superficial sensory loss in the digits. In contrast, 70% presented deep pain diminution, especially in those muscles with diminished deep tendon reflex (except for Hirayama disease) or in those muscles innervated by the same segment with a dysesthetic dermatome. In the patients with spinal neurinoma, deep pain was lost in those muscles with diminished deep tendon reflex. Ten patients of 17 with syringomyelia underwent surgery and complained of residual pain postoperatively in spite of shrinkage of the syrinx. This residual pain was of two types, one being superficial dysesthetic pain and the other muscle aching pain. The latter presumably is related to the dysfunction of the system conveying muscle nociception. Deep pain loss is not uncommon in many spinal cord lesions. In addition, postoperative residual pain in syringomyelia should be recognized as superficial dysesthetic pain, deep muscle aching pain, or both. This approach will develop a successful measure of treatment of residual pain in the future.