Naoto Sakai

Usefulness of Intraoperative Monitoring of Visual Evoked Potentials in Transsphenoidal Surgery

Postoperative visual outcome is a major concern in transsphenoidal surgery (TSS). Intraoperative visual evoked potential (VEP) monitoring has been reported to have little usefulness in predicting postoperative visual outcome. To re-evaluate its usefulness, we adapted a high-power light-stimulating device with electroretinography (ERG) to ascertain retinal light stimulation. Intraoperative VEP monitoring was conducted in TSSs in 33 consecutive patients with sellar and parasellar tumors under total venous anesthesia. The detectability rates of N75, P100, and N135 were 94.0%, 85.0%, and 79.0%, respectively. The mean latencies and amplitudes of N75, P100, and N135 were 76.8 ± 6.4 msec and 4.6 ± 1.8 μV, 98.0 ± 8.6 msec and 5.0 ± 3.4 μV, and 122.1 ± 16.3 msec and 5.7 ± 2.8 μV, respectively. The amplitude was defined as the voltage difference from N75 to P100 or P100 to N135. The criterion for amplitude changes was defined as a > 50% increase or 50% decrease in amplitude compared to the control level. The surgeon was immediately alerted when the VEP changed beyond these thresholds, and the surgical manipulations were stopped until the VEP recovered. Among the 28 cases with evaluable VEP recordings, the VEP amplitudes were stable in 23 cases and transiently decreased in 4 cases. In these 4 cases, no postoperative vision deterioration was observed. One patient, whose VEP amplitude decreased without subsequent recovery, developed vision deterioration. Intraoperative VEP monitoring with ERG to ascertain retinal light stimulation by the new stimulus device was reliable and feasible in preserving visual function in patients undergoing TSS.

Evaluation of tumor blood flow after feeder embolization in meningiomas by arterial spin-labeling perfusion magnetic resonance imaging.

Preoperative embolization changes the amount of blood flow and pattern of flow distribution in meningioma. Tumor blood flow was investigated in eight meningioma patients before and after embolization using arterial spin-labeling (ASL) perfusion imaging. Although blood flow was significantly reduced in the whole tumor after embolization, changes in flow distribution patterns varied from one case to another. The findings suggest that evaluation of post-embolization tumor blood flow by ASL perfusion imaging would be useful in the surgical planning of meningioma.

Cholinergic Dysfunction in Cognitive Impairments after Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE Although cognitive impairments have been observed after subarachnoid hemorrhage (SAH), little is known about their neurobiological bases. To examine cholinergic function in such patients, we used a known test for Alzheimer’s disease based on an exaggerated pupil dilation response to a cholinergic antagonist, tropicamide (the tropicamide drop test). METHODS Seventeen patients who were treated surgically after aneurysmal SAH were divided into two groups on the basis of their scores on the Mini-Mental State Examination (MMSE): Group A (MMSE ≥28) and Group B (MMSE ≤27). The mean interval of time between surgery and administration of the MMSE was 4.7 ± 2.1 years for Group A and 4.2 ± 1.3 years for Group B. The tropicamide drop test was performed within 1 month after the MMSE for each patient. After measurement of the baseline pupil diameter (R1, right pupil size: L1, left pupil size), one drop of 0.01% tropicamide was applied to the right eye and physiological saline to the left eye. Pupil diameter (R2, right pupil size; L2, left pupil size) was then remeasured. Data were represented as the dilation ratio of the right pupil (R2/R1) and as the relative dilation ratio of the right pupil to that of the left pupil (R2L1/R1L2). RESULTS The mean dilation ratio of the right pupil (R2/R1) was higher in Group B (1.13 ± 0.09) than in Group A (1.07 ± 0.11), although the difference did not reach statistical significance (P = 0.18). The relative dilation ratio (R2L1/R1L2) was significantly higher in Group B (1.41 ± 0.36) than in Group A (1.06 ± 0.20) (P < 0.05). CONCLUSION We determined cholinergic dysfunction in patients with cognitive impairment after SAH on the basis of the pupillary response to tropicamide. The results provide an insight into the pathophysiology of cognitive impairments after SAH, which might lead to future treatment strategies.

Absence of Plasma Protease-Antiprotease Imbalance in the Formation of Saccular Cerebral Aneurysms

OBJECTIVE We examined the hypothesis that a plasma protease-antiprotease imbalance contributes to the formation of saccular cerebral aneurysms and the suggestion that the assay of these enzymes might be a screening tool for people at higher risk for aneurysm formation. METHODS From June 1997 through May 1998, the plasma leukocyte elastase, which is an important proteolytic enzyme, and alpha-antitrypsin and alpha2-macroglobulin, which are important antiproteolytic enzyme plasma proteins, were examined in 18 patients with ruptured aneurysms, 9 patients with unruptured aneurysms, and 22 controls. RESULTS The elastase:alpha1-antitrypsin ratio and the elastase:alpha2-macroglobulin ratios were significantly higher in patients with ruptured aneurysms within 24 hours after subarachnoid hemorrhage (SAH) than in the controls. The protease-antiprotease imbalance depended on the elevation of the elastase level, which might be correlated with leukocytosis after SAH. The elastase level decreased to the control level 3 months after the onset of SAH. No significant difference in the elastase:alpha1-antitrypsin and elastase:alpha2-macroglobulin ratios was observed between the patients with unruptured aneurysms and the controls. CONCLUSION These results do not support the hypothesis that a plasma protease-antiprotease imbalance is a potential marker to predict the formation of saccular cerebral aneurysms. The increase in plasma elastase levels in patients with ruptured aneurysms might be attributable to leukocytosis after SAH.

Mixed germ cell tumor and hemangioblastoma in the cerebellum: report of a rare coexistence

We report a case of a cerebellar tumor consisting of a mixed germ cell tumor (GCT) and a hemangioblastoma. A 22-year-old man presented with myoclonus and cerebellar ataxia. Magnetic resonance imaging showed a tumor mass in the left cerebellar hemisphere. The tumor was totally removed, and the histological diagnosis was an undetermined neoplasm. Ten months later, the patient returned with cerebellar hemorrhage at the site of the previous tumor. An emergency craniotomy was performed, and a tumor mass adjacent to the hematoma was resected. Microscopic examination revealed a mixed GCT consisting of a germinoma, choriocarcinoma, and mature teratomatous component. An area of hemangioblastoma was also found in the same tumor mass. A retrospective examination of the histological sample from the first operation indicated a germinoma. A primary GCT of the posterior fossa is very rare, and there are no other reports of the coexistence of a GCT and a hemangioblastoma. A metastatic GCT lesion of extracranial origin should be considered when the intracranial GCT is non-germinomatous and arises in an unusual site. The most probable hypothesis for the histogenesis of this case was a hemangioblastoma complicated by a “tumor-to-tumor” metastatic lesion of testicular GCT with “burnout” of the primary site.

Primary Neurolymphomatosis of the Lower Cranial Nerves Presenting as Dysphagia and Hoarseness: A Case Report

Primary neurolymphomatosis is an extremely rare tumor. We report the case of a 74-year-old patient presenting with dysphagia and hoarseness. Initial contrast-enhanced computed tomography of the head, neck, and chest did not reveal any lesions. His symptoms improved with short-term administration of prednisone but recurred and deteriorated. Magnetic resonance (MR) imaging revealed a tumor along the ninth and tenth cranial nerves across the jugular foramen. Fluorine-18 fluorodeoxyglucose positron emission tomography indicated this was a primary tumor. Repeated MR imaging after 2 months revealed considerable tumor enlargement. A left suboccipital craniotomy was performed to remove the tumor that infiltrated the ninth and tenth cranial nerves. The histopathologic diagnosis was diffuse large B-cell lymphoma. Although focal radiation therapy was administered to ensure complete eradication of the tumor, the patient died of aspiration pneumonia with systemic metastasis. To our knowledge, this is the first reported case of primary neurolymphomatosis in the lower cranial nerves.

Nasopharyngeal carcinoma presenting with rapidly progressive severe visual disturbance: a case report

IntroductionNasopharyngeal carcinoma is one of the most difficult tumors to diagnose correctly at the initial phase because of the occasional lack of nasal symptoms. The perineural spread of the trigeminal nerve is one of the most common and important routes in the intracranial paracavernous extension of nasopharyngeal carcinoma, but visual loss is very rare.Case presentationWe report the case of a 54-year-old Japanese man with nasopharyngeal carcinoma, who presented with rapid and severe disturbance of left monocular visual acuity and eye movement with a 10-month history of ipsilateral otitis media and facial pain. Magnetic resonance imaging revealed a lesion in the left fossa of Rosenmüller, pterygopalatine fossa, sphenoid and ethmoid sinus, and the left cavernous sinus extending to the orbital apex through the superior orbital fissure. The histopathological diagnosis was nonkeratinizing undifferentiated nasopharyngeal carcinoma. Epstein–Barr virus was detected by in situ hybridization. Although focal radiotherapy induced remarkable tumor shrinkage and relieved ocular motor disturbance and facial pain, his visual acuity did not improve.ConclusionThe awareness of cranial nerves in addition to intracranial and orbital apex involvement, as in this case, is important for appropriate diagnosis and treatment planning of nasopharyngeal carcinoma.

Evaluation of the Antiangiogenic Effects of Octreotide on Growth Hormone-producing Pituitary Adenoma using Arterial Spin-labeling Perfusion Imaging

Decreased absolute tumor blood flow (TBF) measured by arterial spin labeling perfusion imaging (ASL-PI) on 3-tesla magnetic resonance imaging demonstrated the reduced size and growth hormone (GH) secretion of a large GH-producing pituitary adenoma in a 32-year-old man in response to octreotide therapy. The study shows the usefulness of ASL-PI in providing a biomarker of the antiangiogenic effect of octreotide.

Dissecting Aneurysm at the Proximal Segment of the Anterior Cerebral Artery Associated with Infraoptic Course Anterior Cerebral Artery

A 48-year-old man presented a subarachnoid hemorrhage caused by a rupture of a dissecting aneurysm at the proximal segment (A1 segment) of the right anterior cerebral artery (ACA). He also had an anomalous artery named infraoptic course ACA and an agenesis of the contralateral ACA A1 segment. Balloon occlusion test at the bifurcation of the right internal carotid artery demonstrated that the distal segments of the bilateral ACAs were perfused through the infraoptic course ACA. Therefore, we surgically trapped the A1 segment including the aneurysm. The patient got discharged without any neurological deficit. Natural course of ACA dissecting aneurysms is unclear because of rarity of the disease and treatment strategy is still controversial. Most of the dissecting aneurysms in the A1 segment are surgically treated, because they often present with massive hemorrhage and poor prognosis. In the present case, the contralateral A1 segment was absent but trapping of the dissecting aneurysm could be achieved without vascular reconstruction (e.g., bypass surgery) because of the presence of the infraoptic course ACA.

Primary Spindle Cell Carcinoma of the Frontal Sinus

Paranasal sinus carcinoma is fairly infrequent, with an incidence of less than 1 per 100,000 persons per year, with the frontal sinus being the primary region in only about 0.3%. The symptoms of paranasal sinus carcinoma are ambiguous and simulate inflammatory diseases, often making it difficult to diagnose these tumors at the advanced stage. Spindle cell carcinoma (SpCC) is also a rare, highly malignant variant of squamous cell carcinoma (SCC) and shows biphasic proliferation of conventional SCC components and malignant spindle-shaped cells with a sarcomatous appearance. We report a rare case of primary SpCC arising in the frontal sinus that was successfully treated by surgical resection. A 71-year-old man complained of painful swelling of the frontal head. A giant solid tumor in the frontal sinus was detected on head computed tomography (CT) and magnetic resonance imaging (MRI), and this tumor was destroying the frontal skull base and invading into the dura, orbit, and ethmoid sinus. The resected specimen consisted of spindle and epithelial cells, which formed nests with prominent keratinization. Histologic examination and immunohistologic analysis of the tumor showed characteristics typical of SpCC. We accordingly diagnosed SpCC in the frontal sinus. Three years after an en bloc resection, the patient is symptom free.