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Junichi Mizuno and Hiroshi Nakagawa

Object

The goal of this study was to determine the appropriate surgical strategy for cervical spondylosis associated with an early form of ossification of the posterior longitudinal ligament (EOPLL) of the cervical spine.

Methods

Patients with EOPLL-associated cervical spondyosis were selected for treatment. Medical records and radiographs were retrospectively reviewed. Specimens taken at the time of operation were histologically examined. There were 24 men and six women ranging in age from 39 to 74 years (mean 57.6 years). Symptoms consisted of myelopathy in 28 cases and radiculopathy in two cases. Anterior decompressive surgery was performed. The EOPLL, hypertrophy of the posterior longitudinal ligament (HPLL), and the disc–PLL complex were directly resected. The mean preoperative Japan Orthopaedic Association score was 12.6, and the mean postoperative score was 14.4. Histologically, EOPLL was consistent with foci of compact lamellar bone in the degenerative thickening of the PLL.

Conclusions

Appropriate corpectomy should follow direct removal of EOPLL associated with HPLL compressing the spinal cord to achieve good outcomes.

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Junichi Mizuno, Hiroshi Nakagawa, Tatsushi Inoue, and Yoshio Hashizume

Object. The goal of this study was to elucidate the pathophysiological features and clinical significance of the magnetic resonance imaging—documented small intramedullary high signal intensity known as “snake-eye appearance” (SEA) in cases of compressive myelopathy such as cervical spondylosis or ossification of the posterior longitudinal ligament.

Methods. One hundred forty-four patients with compression myelopathy who underwent surgery between 1998 and 2000 were selected. Intramedullary high signal intensity was found in 79 cases and was divided into two types, SEA and non-SEA (NSEA). The Japan Orthopaedic Association (JOA) scoring system was used for evaluation of pre- and postoperative neurological status. In nine cases of SEA autopsy was performed and specimens were histologically analyzed.

The improvement ratio determined by JOA score was 32.2 ± 15.1% in SEA, 47.1 ± 12.1% in NSEA, and 50 ± 18.3% (p < 0.01) in control cases in which high signal intesity was absent. There were significant differences among SEA, NSEA, and control groups. In a separate group of nine patients who died of unrelated causes, histological examination showed small cystic necrosis in the center of the central gray matter of the ventrolateral posterior column and significant neuronal loss in the flattened anterior horn.

Conclusions. Snake-eye appearance was found to be a product of cystic necrosis resulting from mechanical compression and venous infarction. Destruction of the gray matter accompanying significant neuronal loss in the anterior horn suggested that SEA is an unfavorable prognostic factor for the recovery of upper-extremity motor weakness.

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Han Soo Chang, Kazuhiro Hongo, and Hiroshi Nakagawa

Object. This study was aimed at clarifying the effect of intraoperative hypotensive anesthesia on the outcome of early surgery in patients with subarachnoid hemorrhage (SAH) caused by saccular cerebral aneurysms. Other factors were also screened for possible effects on the outcome.

Methods. Hospital charts in 84 consecutive patients with SAH who underwent aneurysm clipping by Day 4 were examined. Possible factors affecting the outcome were analyzed using multiple logistic regression with the dichotomous Glasgow Outcome Scale score as the outcome variable. The relationship between the intraoperative hypotension and the occurrence and severity of vasospasm was studied using both single- and multivariate analyses.

Conclusions. Intraoperative hypotension had a significantly adverse effect on the outcome of SAH. Hypotension was also related to more frequent and severe manifestations of vasospasm. A long-lasting effect of brain retraction is possibly the cause of this phenomenon. The data contained in this study preclude the use of intraoperative hypo- tension even in a limited form.

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Yutaka Sawamura, Yoku Nakagawa, Toshio Ikota, and Hiroshi Abe

✓ Neurinomas arising from the peripheral branch of the acoustic nerve distal to the internal auditory canal in the temporal bone are rare. Two advanced skull-base neurinomas are described which were situated mainly in the temporal petrous bone, and extended to the parapharyngeal space anteriorly, to the lateral cervical portion inferiorly, into the sphenoidal sinus medially, and into the middle and posterior cranial fossae compressing the brain stem. Both patients had been deaf for several years without other neurological deficits. The operative findings revealed that the fifth, seventh, and caudal cranial nerves were intact; therefore, it was suspected that these neurinomas originated primarily within the cochlea or the vestibule in the temporal bone. The tumors were completely removed via an extradural approach, with good results. Since the surgical treatment of such advanced skull-base neurinomas is difficult, the operative infratemporal fossa approach is described in detail.

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Junichi Mizuno, Hiroshi Nakagawa, Naoki Matsuo, and Joonsuk Song

Object. The authors' goal in this study was to understand the frequency and pattern of dural ossification (DO, and to evaluate the effectiveness of neuroimaging modalities used to identify this disease in association with ossification of the posterior longitudinal ligament (OPLL).

Methods. One hundred eleven patients with OPLL underwent anterior procedures. Of these patients, 17 (15.3%) had associated ossification of the dura mater. There were 10 cases of DO in the 94 patients with segmental OPLL and seven in the 17 patients with nonsegmental OPLL (seven continuous and 10 mixed-type OPLL). Retrospective evaluation of DO was performed by examining plain x-ray films, polytomography studies, computerized tomography (CT) scans, and magnetic resonance (MR) images. A positive correlation was found between the type of OPLL and the frequency of DO (p < 0.01).

The DO was classified into the following three types according to shape: 1) isolated type, 2) double-layer type, and 3) en bloc type, based on its relationship with OPLL. There were 10 lesions of the double-layer type, four en bloc type, and three isolated type; the double-layer pattern of DO was the most common. All DOs as well as OPLLs (17 cases) were identified using bone-window CT scanning. Polytomography was used successfully to identify all 12 OPLLs, whereas DO was recognized in seven of the 12 cases. Magnetic resonance imaging could not identify DO (none of the 17 cases), although OPLL was identified on MR imaging in 12 of the 17 cases.

Conclusions. Three patterns of DO associated with OPLL, that is, isolated, double-layer, and en bloc types, were confirmed by retrospective analysis of neuroimaging findings. Nonsegmental OPLL was likely to be accompanied by DO. Bone-window CT scanning was most useful for identification of DO as well as OPLL, whereas MR imaging was ineffective in recognizing DO.

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Junichi Mizuno and Hiroshi Nakagawa

Object

This study was designed to determine the surgical technique and surgery-related outcome, fusion rate, and complication of anterior decompression and fusion (with various graft materials) performed in patients with ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

Methods

Between 1980 and 1998, 107 patients with radiologically proven OPLL underwent surgery via the anterior approach for direct removal of the ossified mass. Graft materials included iliac crest in 45 cases, vertebral body (VB) in 37 cases; and interbody fusion cages in 25 cases. In four patients with three-level VB grafts and one with a two-level VB graft, anterior plates were placed. Surgery-related outcome was excellent or good in 89% and fair in 11%. This clinical improvement correlated well with the severity of preoperative myelopathy. Only one patient with severe myelopathy due to extensive mixed-type OPLL developed a segmental weakness of the bilateral upper extremities. The overall fusion rate was 97%. Three patients with obvious spinal instability due to pseudarthrosis required reoperation. Of the graft materials used in this series, VB grafts were the most fragile.

Conclusions

The anterior approach is an effective route for decompressing the cervical cord with OPLL. Slight asymptomatic kyphotic deformity may be encountered. Of the graft materials used in our series, VB graft was considered most fragile, and thus least optimal.

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Kouhei Echizenya, Masaharu Satoh, Tango Nakagawa, Mitsuyuki Koiwa, and Hiroshi Abe

✓ The authors report two cases of bitemporal compression injury caused by a static loading mechanism. These head injuries resulted from gradual bitemporal compression of the head. Plain skull films showed multiple skull fractures, and carotid angiography revealed internal carotid artery obstruction at the base of the skull. Neurological examination disclosed a slight disturbance of consciousness, hemiparesis, multiple cranial nerve injuries, and Horner's syndrome. In comparison with impact head injury, the energy from this type of trauma tends to be transmitted to the foramina and hiati of the middle cranial fossa and results in multiple injuries to the cranial nerves, sympathetic nerves, and blood vessels.

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Han Soo Chang, Masahiro Joko, Naoki Matsuo, Sang Don Kim, and Hiroshi Nakagawa

✓ The pathophysiology of syringomyelia is still not well understood. Current prevailing theories involve the assumption that cerebrospinal fluid (CSF) flows into the syrinx from the subarachnoid space through the perivascular space of Virchow—Robin. Reported here is the case of a patient with syringomyelia in which this course is clearly contradicted.

This patient with a holocord syrinx associated with adhesive arachnoiditis was treated 3 years previously with insertion of a subarachnoid—peritoneal shunt and had recently experienced worsening myelopathy. On surgical exploration, the shunt system was functioning normally. The medium-pressure shunt valve was replaced with an adjustable valve with a higher closing pressure setting, thus increasing the CSF pressure in the subarachnoid space. Contrary to prevailing theories, this procedure markedly reduced the size of the syrinx.

This case provides direct evidence that the syrinx size is inversely related to subarachnoid CSF pressure and supports the hypothesis that the pressure gradient across the spinal cord parenchyma is the force that generates syringes in syringomyelia.

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Hiroshi Nakagawa, Sang-Don Kim, Junichi Mizuno, Yukoh Ohara, and Kiyoshi Ito

Object. The authors discuss the safety and efficacy of an ultrasonic bone curette in various spinal surgeries and report its advantages in clinical application.

Methods. Between April 2002 and September 2003, 76 patients with various spinal diseases (29 cervical, five thoracic, 40 lumbosacral, and two foramen magnum regions) were treated microsurgically by using a Sonopet ultrasonic bone curette with longitudinal and torsional tips and lightweight handpieces. The operations were performed successfully and the device was easy to handle. There were no instrument-related complications or -induced damage to any structure even when removing osseous spurs or ossified lesions near the dura mater, nerves, and vessels.

Conclusions. The ultrasonic curette is a useful instrument for procedures performed near the dura mater or other neural tissue without excessive heat production or mechanical injury. This device is recommended for various spinal surgeries in addition to high-speed drills or other tools.