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Kazutoshi Hida and Yoshinobu Iwasaki

Object

The authors describe the surgical procedures for placing syringosubarachnoid shunts and the results of surgery, as well as the prevention of shunt malfunction.

Methods

The series consisted of 59 patients with syringomyelia associated with Chiari I malformation in whom syringosubarachnoid shunts were placed. Their ages ranged from 4 to 62 years (median 28 years). The follow-up period ranged from 13 to 219 months. The authors principally implanted the shunts in patients with large-sized syringes. Neurological improvement was satisfactory, and postoperative magnetic resonance imaging demonstrated that the syringes had resolved or decreased in size in all patients. Reoperation was necessary in 10 patients who were treated before 1993.

Conclusions

To prevent shunt malfunction, both dorsal root entry zone myelotomy and placement of the syringo-subarachnoid shunt tube into the ventral subarachnoid space are useful.

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Kazutoshi Hida, Yoshinobu Iwasaki and Minoru Akino

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Jangbo Lee, Kazutoshi Hida, Toshitaka Seki and Yoshinobu Iwasaki

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Izumi Koyanagi, Yoshinobu Iwasaki, Kazutoshi Hida, Hiroyuki Imamura and Hiroshi Abe

Object. Because of the lack of magnetic resonance (MR) signal from cortical bones, MR imaging is inadequate for diagnosing ossified lesions in the spinal canal. However, MR imaging provides important information on spinal cord morphology and associated soft-tissue abnormality. The purpose of this study is to determine the role of MR imaging in the diagnosis and treatment of patients with ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

Methods. The authors reviewed MR imaging findings in 42 patients with cervical OPLL who were examined with a superconducting MR imaging system. The types of OPLL reviewed included eight cases of continuous, 21 cases of segmental, and 13 cases of the mixed type. All patients were treated surgically either by anterior (26 cases) or posterior decompression (16 cases).

Conclusions. The T1-weighted images clearly demonstrated the spinal cord deformity caused by OPLL. Associated disc protrusion was found to be present at the maximum compression level in 60% of the patients in this series. The highest incidence of disc protrusion (81%) was found in patients with segmental OPLL. Intramedullary hyperintensity on T2*-weighted imaging was noted in 18 patients (43%). The neurological deficits observed in these 18 patients were significantly more severe than those observed in the other 24 patients. Postoperative MR imaging revealed improvement in the spinal cord deformity, although the intramedullary hyperintensity was still observed in most cases. The present study demonstrates the importance of associated disc protrusion in the development of myelopathy in patients with cervical OPLL. Magnetic resonance imaging findings may be used to help determine the actual levels of spinal cord compression and to suggest the method of surgical treatment.

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Kazutoshi Hida, Yoshinobu Iwasaki, Katsuya Goto, Kazuo Miyasaka and Hiroshi Abe

Object. This retrospective study was performed to evaluate the results of surgical treatment and the use of preoperative embolization in managing patients with perimedullary arteriovenous fistulas (AVFs).

Methods. The authors studied 20 consecutive patients with perimedullary AVFs who underwent surgical treatment. Arteriovenous shunts were at the level of the cervical spine in five patients, the thoracic spine in 12, and the conus medullaris in three patients. Of the 20 AVFs, three were fed by the anterior spinal artery only, three by the posterior spinal artery, and 14 by both the anterior and posterior spinal arteries. Nine patients had varices that compressed the spinal cord. Eleven patients underwent surgery, and nine patients underwent surgery combined with adjuvant preoperative embolization.

Preoperative embolization remarkably reduced blood flow through the AVFs and facilitated subsequent surgical procedures. Postoperative angiography revealed complete disappearance of the AVFs in 16 patients. However, small fistulas persisted in the other four patients, whose large lesions were fed by the anterior spinal artery. Postoperatively, neurological status was improved in 11 patients, unchanged in eight, and worse in one patient.

Conclusions. Effective interruption of a spinal arteriovenous shunt was achieved by surgery in all cases, even when the anterior spinal artery was involved. For large and high-flow AVFs, embolization proved to be a useful adjunct to surgery.

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Kazutoshi Hida, Yoshinobu Iwasaki, Katsuya Goto, Kazuo Miyasaka and Hiroshi Abe

This retrospective study was performed to evaluate the results of surgical treatment and the use of preoperative embolization in managing perimedullary arteriovenous fistulas (AVFs).

The authors studied 20 consecutive patients with perimedullary AVFs who underwent surgical treatment. Arteriovenous shunts were at the level of the cervical spine in five patients, the thoracic spine in 12, and the conus medullaris in three patients. Of the 20 AVFs, three were fed by the anterior spinal artery only, three by the posterior spinal artery, and 14 by both the anterior and posterior spinal arteries. Nine patients had varices that compressed the spinal cord. Eleven patients underwent surgery alone, and 9 patients underwent surgery combined with adjuvant preoperative embolization.

Preoperative embolization remarkably reduced the blood flow through AVFs and facilitated subsequent surgical procedures. Postoperative angiography revealed complete disappearance of the AVF in 16 patients. However, small fistulas persisted in the other four patients whose large lesions were fed by the anterior spinal artery. Neurological status was improved in 11 patients, unchanged in eight, and worse in one patient postsurgery.

Effective interruption of a spinal AV shunt was obtained by surgery in all cases, even when the anterior spinal artery was involved. For large and high-flow AVFs, embolization proved to be a useful adjunct to surgery.

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Ken Sakushima, Kazutoshi Hida, Ichiro Yabe, Satoshi Tsuboi, Ritei Uehara and Hidenao Sasaki

Object

Syringomyelia is a rare disease commonly caused by Chiari I malformation. Surgery by neurosurgeons and orthopedists is a critical treatment for symptomatic patients, and surgical techniques are associated with improved symptoms for these patients. The aim of this study was to determine the different surgical techniques used by neurosurgeons and orthopedists in Japan to treat syringomyelia caused by Chiari I malformation.

Methods

Patients who had undergone a surgical treatment were identified from a 2-stage postal survey conducted in late 2009. The authors compared the type of surgery performed and its association with cavity size reduction, on the basis of whether patients were receiving care in a neurosurgery or orthopedics department.

Results

A total of 232 patients with syringomyelia caused by Chiari I malformation were included in this study. Two-thirds of patients were treated in a neurosurgery department and the other third in an orthopedics department. Neurosurgeons preferred foramen magnum decompression (FMD) with dural patch grafting, and orthopedists preferred FMD with dural dissection. Foramen magnum decompression with dural patch grafting was associated with better outcomes than was dural dissection with regard to the following: motor impairment (66% vs 39%, p < 0.05), sensory disturbance (60% vs 43%, p = 0.051), pain (67% vs 47%, p < 0.05), and cavity size (74% vs 58%, p < 0.05). Improved motor function was associated more with cavity size reduction than with sensory disturbance and pain.

Conclusions

Surgical procedures and outcomes differed, depending on whether the patient's care was managed in a neurosurgery or orthopedics department. Outcomes were better after FMD with dural patch grafting.

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Ki Hong Cho, Yoshinobu Iwasaki, Hiroyuki Imamura, Kazutoshi Hida and Hiroshi Abe

✓ An experimental model was devised to elucidate the role of spinal blockade in posttraumatic syringomyelia. Thirty-eight Japanese White rabbits, each weighing about 3 kg, were used in this study. The animals were divided into four groups: in Group 1, eight animals received traumatic injury only; in Group 2, 12 animals received traumatic injury following injection of 100 mg kaolin suspended in 1 cc normal saline solution into the subarachnoid space at the site of trauma; in Group 3, nine animals received traumatic injury following injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space at the site of trauma; and in Group 4, nine animals without traumatic injury received an injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space.

The subjective criteria for syrinx formation were the presence of a definite round cyst having a smooth margin and an upper or lower extension of more than 2 cm from the injured site. Syrinx formation was seen in 12.5% (one of eight rabbits) in Group 1, 41.7% (five of 12 animals) in Group 2, 55.5% (five of nine rabbits) in Group 3 and 0% (none of nine animals) in Group 4 (p < 0.05). There was a tendency for the combined trauma/kaolin injection groups to be more prone to develop a syrinx. In the kaolin injection only group (Group 4), no animal showed a definite cyst or an extending cavity during the experimental period. The results suggest that kaolin enhances the extension of multiple small cavities that have already formed at the time of initial injury. The difference between the frequency of syrinx formation and the time of survival was statistically significant well beyond the 0.05% level. The overall difference, relating to the frequency of syrinx development, group, and duration of survival, was also statistically significant. In summary, subarachnoid block secondary to adhesive arachnoiditis is important in initiating the extension of the syringomyelia cavity.

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Satoshi Yamaguchi, Kazutoshi Hida, Masaaki Takeda, Takafumi Mitsuhara, Mizuki Morishige, Naoto Yamada and Kaoru Kurisu

Surgical lysis of the thickened arachnoid membrane is the first choice of treatment in spinal arachnoid pathologies that cause flow disturbances or blockage of CSF. However, it is important to consider that while extensive lysis of the arachnoid may temporarily provide a wide pathway for CSF, an extensive lytic procedure may later cause secondary adhesion. Thus, it is ideal for the proper extent of the arachnoid lysis to be determined after careful analysis of regional CSF flow. The authors report their limited experience with intraoperative visualization of CSF flow in spinal arachnoid pathologies. Two patients with a dorsal arachnoid web (DAW) with cervical syringomyelia and 1 patient with focal adhesive arachnoiditis causing edema of the spinal cord were surgically treated at the authors' institution between 2007 and 2013. In all cases, the presence of a DAW or focal adhesive arachnoiditis was suspected from the findings on MRI, namely 1) an indentation on the upper thoracic spinal cord and 2) syringomyelia and/or edema of the spinal cord above the indentation. Exploratory surgery disclosed a transversely thickened arachnoid septum on the dorsal side of the indented cord. To prove blockage of the CSF by the septum and to decide on the extent of arachnoid lysis, regional CSF flow around the arachnoid septum was visualized by subarachnoid injection of gentian violet solution close to the web. Injected dye stagnated just close to the arachnoid septum in all cases, and these findings documented CSF blockage by the septum. In 2 cases, a 2-minute observation showed that the injected dye stayed close to the web without diffusion. The authors performed not only resection of the web itself but also lysis of the thickened arachnoid on both sides of the spinal cord to make a CSF pathway on the ventral side. In the third case, the dye stagnated close to the web at first but then diffused through the nerve root to the ventral CSF space. The lysis procedure was completed after exclusive removal of the dorsal web. Postoperative MR images confirmed reduction of the syrinx and/or improvement of the edema in all cases, suggesting that the extent of arachnoid lysis was optimal in each case. No adverse effect was observed after subarachnoid injection of gentian violet. The authors believe that their technique of visualizing regional CSF flow will be helpful to decide the optimal extent of lysis in some local arachnoid pathologies.

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Shuji Hamauchi, Toshiya Osanai, Toshitaka Seki, Masahito Kawabori, Michinari Okamoto, Kazutoshi Hida and Kiyohiro Houkin

The authors describe a novel method of observing blood flow in abnormal vessels with slow-motion video during surgical treatment of spinal arteriovenous shunts. The method is based on the use of superselective angiography with saline for visualizing abnormal vessels in bright field and commercially available high frame rate digital camera for recording slow-motion video.