Shokei Yamada

Extensibility of the lumbar and sacral cord. Pathophysiology of the tethered spinal cord in cats.

Tethered spinal cord, or tethered cord syndrome, describes a disorder manifested by progressive motor and sensory deficit in the legs and by incontinence. Tethered cord syndrome occurs when the elongated spinal cord is anchored by a thick filum terminale or other pathological structures. The underlying mechanism is impairment of oxidative metabolism in the lumbosacral cord. The authors studied the extensibility of various parts of lumbar, sacral, and coccygeal segments in experimental animals and correlated this with the oxidative metabolism in these segments. The filum terminale possesses far greater extensibility than any spinal cord segments and functions as a buffer in preventing the cord from overstretching. The lumbar, sacral, and coccygeal segments elongate under traction only below the attachment of the lowest pair of dentate ligaments. The lower the cord segment, the greater the percentage of elongation in spite of limited elasticity of the cord tissue; this greater percentage of elongation of the spinal cord correlates with increasing impairment of the oxidative metabolism and more severe neurological deficit. These findings explain such symptoms and signs as motor and sensory deficits in the legs associated with the human tethered cord syndrome, and correspond with the high clinical incidence of incontinence. The lower spinal cord segments elongated promptly within 3 seconds after the start of traction. This implies that repeated acute hyperextension and hyperflexion, as occurs in humans, may accentuate oxidative metabolic changes that have already been caused by chronic cord tethering. The authors conclude that the elongation of the spinal cord under traction parallels the degree of metabolic dysfunction.

Pathophysiology of tethered cord syndrome and other complex factors

Abstract There are different interpretations of tethered cord syndrome (TCS) partly due to difficulty in understanding the concept of this syndrome as a functional disorder not merely based on gross anatomy of congenital anomalies. The essential mechanical factor of cord tethering is that any of the inelastic structures fastening the caudal end of the spinal cord produces traction effects on the lumbosacral cord. The production of such traction is the key to understanding this disorder. In a significant number of patients who present with the typical clinical signs and symptoms of TCS, the diameter of the filum terminale is found within normal limits and the caudal end of the spinal cord is located in the normal position. Therefore, the definition of TCS requires the demonstration that there is a posterior displacement of the conus and filum by MRI, lack of viscoelasticity by the stretch test of the filum during surgery, and fibrous displacement of glial tissue within the filum by histological studies. This is because there is inconsistency from such studies as ultrasonography, MRI and CT myelography, which attempt to establish the presence of a tight filum terminale. A goal of this article is to provide basic understanding of TCS so that clinicians can use the concept of stretch-induced spinal cord dysfunction for proper diagnosis and treatment of this disorder.

Fibroblast growth factor receptor (FGFR) 4 correlated with the malignancy of human astrocytomas

Abstract Fibroblast growth factor receptor (FGFR) 4 possesses high affinity to acidic and basic fibroblast growth factors (FGFs). The authors focused on FGFR 4 expression in astrocytoma because the FGF expression increases as the tumor malignancy progresses. Forty-one astrocytoma specimens were examined by immunohistochemistry and polymerase chain reaction-Southern blot. FGFR 4 was negative in all seven Grade II astrocytomas by immunohistochemistry, while positive in four among 15 Grade III and in 13 among 19 Grade IV astrocytomas. The median survival time of Grade III astrocytoma patients was 22.3 months in FGFR 4 negative group and 14.5 months in positive group (p < 0.05). Those of Grade IV patients were 14.2 months in FGFR 4 negative group and 11.9 months in positive group (p > 0.05, not significant). However, FGFR 4 mRNA was detected in all specimens suggesting activated translation system of FGFR 4 in progression of the tumor malignancy. Histologically diagnosed Grade III astrocytoma patients can be divided into two groups; one with median survival time close to those with Grade II astrocytoma patients, and the other similar to that of glioblastoma patients. The authors concluded that FGFR 4 must be an important factor which predicts short survival Grade III astrocytoma patients, who require strict adjuvant therapy in accordance with glioblastoma. [Neurol Res 2002; 24: 244-248]

Arteriovenous Malformations in the Functional Area: Surgical Treatment and Regional Cerebral Blood Flow

Total resection of the arteriovenous malformation (AVM) is the procedure of choice. The author presents 18 cases of AVMs located in the functional areas. In 16 of these cases, the AVM was totally eliminated and the remaining two radically subtotally eliminated. It is the authors belief that the technical innovation applied to the surgical procedure in the management of AVMs is responsible for the absence of a mortality factor. The high quality of the neurological improvement, and the patients ability to resume a normal life are also attributed to this new approach. A significant postoperative improvement in the rCBF was compared to the postoperative improvement in neurological status and activities.

Stimulation of the globus pallidus in Parkinson's disease.

In 62 patients undergoing posteroventral pallidotomy (PVP) for the treatment of Parkinsons disease, we have demonstrated significant (p < 0.01) elimination of akinetic features and other symptoms during intraoperative stimulation trials in areas anterior to the PVP target (n = 30). Stimulation in anterior pallidal regions frequently resulted in an immediate reversal of akinetic states despite enforced abstinence of medications. The beneficial effects were achieved with as little as 0.25 V at 100 Hz. Stimulation at the PVP target site (n = 32) resulted in insignificant changes (p > 0.05).

Tethered cord syndrome: overview of diagnosis and treatment

Abstract This article covers the basis of tethered cord syndrome as a stretch-induced spinal cord disorder, including pathophysiology, signs and symptoms, imaging diagnosis, indication for surgical treatment, and surgical procedures. Anomalies that cause mechanical spinal cord tethering are listed, and the surgical untethering technique for each anomaly is described.

Pineal Tumors and Associated Lesions: The Effect of Ethnicity on Tumor Type and Treatment

Pineal region lesions consist of a wide variety of rare tumor types, including deep midline cysts, intrinsic pineal tumors, germ cell tumors and vascular lesions. Advances in microsurgical, endoscopic and stereotactic techniques have helped to lower morbidity and mortality in the care of patients harboring these lesions. Surgery can be the definitive treatment in cysts and benign lesions. This report summarizes the retrospective experience of the authors with 64 pineal region and associated lesions encountered in multiple institutions over the last 20 years. Histology was obtained in 53 out of 64 radiographically apparent lesions. Direct surgical biopsy of solid and vascular tumors in the pineal region enables precise histological assessment of mixed tumors. By avoiding sampling error, precise treatment can be planned. This series, along with previously published data, shows a much higher incidence of intrinsic pineal tumors, glial tumors and nongerminomatous germ cell tumors in series from North America and Europe than in those from Japan and Korea, where germinoma is much more common. We experienced an incidence of 20.4% germinoma out of 49 solid and vascular pineal tumors, while other authors have described incidences of 51.2 and 53.5%, respectively. The fact that histology is more diverse in Western populations leads to a need to have more representative sampling. Early surgical resection combined with diversion of cerebrospinal fluid is effective in the treatment of pineal lesions and seems to be superior to the alternative of treatment based on the diagnostic response to radiation and/or on tumor markers alone.

What is the true tethered cord syndrome

IntroductionThe tethered cord syndrome (TCS) is a stretch-induced functional disorder of the spinal cord with its caudal part anchored by an inelastic structure.DiscussionThis article clarifies the reversible lesions that occur in the cord segments above any of the inelastic abnormalities. These lesions are found mostly in the lumbosacral cord, occasionally in the cervical cord and closely correlate with clinical findings. Imaging studies alone do not allow accurate diagnosis of the TCS. The authors emphasize the importance of adhering to the physiological terms “tethered cord syndrome” and “tethered spinal cord” to avoid controversies derived from terms that are not based on the pathophysiology of TCS.

New pathophysiology of Parkinson’s disease revealed by posteroventral pallidotomy

Since the failure of levodopa therapy to maintain long-term symptom relief in Parkinsons disease, posteroventral pallidotomy has seen a dramatic increase in use and interest. It has significantly reduced both the akinetic and hyperkinetic symptoms of Parkinsons disease while requiring most patients to maintain preoperative levodopa doses. Here we review the clinical results of over 300 posteroventral pallidotomies and pathophysiology of Parkinsons disease in relationship to different neurotransmitters and medical therapy.

Concept of arteriovenous malformation compartments and surgical management

Abstract Cerebral AVMs are known to be a source of intracranial hemorrhages and epileptic seizures. Their natural history indicates approximately 15% mortality and 35% morbidity over a 15-year period. This significant mortality and morbidity mandates a need for satisfactory treatment of this entity, ideally by elimination of AVMs. Microsurgical resection, endovascular embolization and radiosurgery (irradiation) are the three effective modes of treatment currently available. However, no objective criteria have been established for which mode(s) of treatment should be selected for individual patients with AVMs. Considering the complexity of AVMs and variable conditions of individual patients, neurosurgeons, intravascular interventionalists and radiosurgeons must make their own decisions on how to treat each patient based on their experience. In practice, treatment of small AVMs in non-functional areas is favored equally by each of these specialists, while they tend to avoid treatment of large AVMs, particularly those in functional areas of the brain. The authors report the surgical intervention of large AVMs, including those located in functional areas of the hemisphere by special techniques. One can demonstrate AVM compartments by using angiography and with the aid of color Doppler ultrasonography, each compartment can be outlined and dissected individually until all the compartments are isolated without causing any damage to the surrounding brain and the entireAVM is rendered shrunken and then removed. The concept of compartmental treatment of AVMs may be applied in the future to radiosurgery and intravascular embolization of large AVMs.