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Tetsuo Hayashi, Takayoshi Ueta, Masahiro Kubo, Takeshi Maeda and Keiichiro Shiba

Object

The origin of posttraumatic syringomyelia is not completely understood. With respect to posttraumatic syringomyelia, the optimum management strategy for patients with spinal cord injury has also not been established. The authors hypothesized that reconstruction of the subarachnoid channels would reestablish CSF flow, thereby addressing the underlying cause of the syrinx formation. The authors performed a new type of surgery, subarachnoid–subarachnoid bypass (S–S bypass), in which an attempt was made to reestablish normal CSF circulation around the spinal cord. The purpose of this study was to evaluate the effectiveness of S–S bypass for posttraumatic syringomyelia.

Methods

Twenty consecutive patients with symptomatic posttraumatic syringomyelia who had progressive neurological symptoms and underwent S–S bypass were included in the study. The surgical procedure was as follows: a laminectomy was performed at the level of trauma, and a midline dural opening was made under a microscope. The arachnoid was exposed up to the area of normal arachnoid mater with normal CSF circulation. After dissection of the normal arachnoid mater at the cephalic and caudal sites, 1 or 2 tubes made of medical-grade silicone were inserted into the cephalic and caudal ends of the normal subarachnoid space. Bypass tubes were laid in the subdural space, and a watertight dural closure was accomplished using running sutures. The mean follow-up period was 48.2 months (range 12–93 months). The preoperative status and postoperative clinical course were assessed according to 3 grading systems: the Frankel grading system for global neurological status, the American Spinal Injury Association motor score for motor weakness, and the Klekamp system for bladder function. The major presenting symptoms or signs were assessed in terms of symptom improvement, stabilization, or deterioration. Preoperative and postoperative MRI was used to analyze the size and craniocaudal extension of the cavity.

Results

Twelve patients showed clinical improvement, 4 were stable, and 4 showed deterioration. The mean length of the syrinx observed on preoperative MRI was 9.9 spinal levels, and the mean Vaquero index was 62.3%. The mean length of the syrinx observed on postoperative MRI was 5.3 spinal levels, and the mean Vaquero index was 28.4%. These values were significantly lower than the preoperative values (p = 0.01 and p < 0.01, respectively).

Conclusions

This study showed that interference with CSF flow was the major cause of syrinx development and that reconstruction of CSF flow is the most important treatment strategy based on the cause of the syrinx. Subarachnoid–subarachnoid bypass, which can be performed without myelotomy, was not only a safe and effective surgical technique, but may also be a more physiological way of treating posttraumatic syringomyelia.

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Minoru Hayashi, Shinobu Marukawa, Hiroyuki Fujii, Tetsuo Kitano, Hidenori Kobayashi and Shinjiro Yamamoto

✓ Simultaneous continuous recording of intracranial pressure (ICP) and systemic blood pressure was carried out in 26 patients admitted within 1 week after subarachnoid hemorrhage (SAH) due to a ruptured intracranial aneurysm. The patients were graded as described by Hunt and Hess. Recordings were made for 1 to 5 days. The more impaired the consciousness, the higher the rate of ICP. In Grade III, IV, and V patients, the mean ICP level was in the range of 15 to 40 mm Hg, 30 to 75 mm Hg, and exceeded 75 mm Hg, respectively. A definite correlation between vasospasm shown by cerebral arteriogram and the clinical grade was not observed. In our series of ICP recordings, we never observed a typical plateau wave. The variations of ICP seen in Grade III and IV patients were the B- and C-waves (15 to 45 mm Hg in amplitude) described by Lundberg, and those in Grade V patients were the high amplitude monotonous waves synchronous with the arterial pulses (15 to 40 mm Hg in amplitude). These phenomena may indicate that Grade III and IV patients with SAH are in a condition of cerebral vasomotor instability, and Grade V patients have cerebral vasomotor paralysis.

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Minoru Hayashi, Hidenori Kobayashi, Hirokazu Kawano, Yuji Handa, Shinjiro Yamamoto and Tetsuo Kitano

✓ Intracranial pressure (ICP) was continuously recorded, isotope cisternography was performed, and the ventricular system size was evaluated on serial computerized tomography scans in 39 patients. All of these patients had communicating hydrocephalus after subarachnoid hemorrhage (SAH) from rupture of an intracranial aneurysm. The studies were carried out in both the acute stage (within 7 days after SAH) and the communicating hydrocephalus stage. In patients in the acute stage who had no ventricular dilatation, but who later developed communicating hydrocephalus, the resting ICP was high, and an ICP pattern of B-wave activity was seen; there was no delay in cerebrospinal fluid (CSF) absorption on isotope cisternography. Patients with communicating hydrocephalus in whom ICP recordings were started within 63 days after SAH had a pattern of plateau waves in conjunction with B-waves, and there was a marked delay in CSF circulation. In general, patients with higher resting ICP's had more frequent ICP irregularities. Patients with communicating hydrocephalus in whom recordings were begun more than 6 months after SAH had a low and flat ICP pattern, and there was no delay in CSF absorption in spite of bilateral convexity blocks on isotope cisternography. The results suggest that the ICP pattern of plateau waves in conjunction with B-waves can be regarded as a sign of delayed CSF absorption; hence, shunting procedures may be indicated in patients with plateau waves in conjunction with B-waves visualized on continuous ICP recordings.

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Tetsuo Hayashi, Elizabeth L. Lord, Akinobu Suzuki, Shinji Takahashi, Trevor P. Scott, Kevin Phan, Haijun Tian, Michael D. Daubs, Keiichiro Shiba and Jeffrey C. Wang

OBJECTIVE

The efficacy of some demineralized bone matrix (DBM) substances has been demonstrated in the spinal fusion of rats; however, no previous comparative study has reported the efficacy of DBM with human mesenchymal stem cells (hMSCs). There is an added cost to the products with stem cells, which should be justified by improved osteogenic potential. The purpose of this study is to prospectively compare the fusion rates of 3 different commercially available DBM substances, both with and without hMSCs.

METHODS

Posterolateral fusion was performed in 32 mature athymic nude rats. Three groups of 8 rats were implanted with 1 of 3 DBMs: Trinity Evolution (DBM with stem cells), Grafton (DBM without stem cells), or DBX (DBM without stem cells). A fourth group with no implanted material was used as a control group. Radiographs were obtained at 2, 4, and 8 weeks. The rats were euthanized at 8 weeks. Overall fusion was determined by manual palpation and micro-CT.

RESULTS

The fusion rates at 8 weeks on the radiographs for Trinity Evolution, Grafton, and DBX were 8 of 8 rats, 3 of 8 rats, and 5 of 8 rats, respectively. A significant difference was found between Trinity Evolution and Grafton (p = 0.01). The overall fusion rates as determined by micro-CT and manual palpation for Trinity Evolution, Grafton, and DBX were 4 of 8 rats, 3 of 8 rats, and 3 of 8 rats, respectively. The Trinity Evolution substance had the highest overall fusion rate, however no significant difference was found between groups.

CONCLUSIONS

The efficacies of these DBM substances are demonstrated; however, the advantage of DBM with hMSCs could not be found in terms of posterolateral fusion. When evaluating spinal fusion using DBM substances, CT analysis is necessary in order to not overestimate fusion.

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Tetsuo Hayashi, Michael D. Daubs, Akinobu Suzuki, Trevor P. Scott, Kevin H. Phan, Monchai Ruangchainikom, Shinji Takahashi, Keiichiro Shiba and Jeffrey C. Wang

OBJECT

Most studies of Modic changes (MCs) have focused on investigating the relationship between MCs and lowback pain, whereas the kinematic characteristics and degenerative disc disease associated with MCs are not well understood. To the authors' knowledge, no previous study has reported on the kinematics of MCs. The purpose of this study was to elucidate the relationship of MCs to segmental motion and degenerative disc disease.

METHODS

Four hundred fifty symptomatic patients underwent weight-bearing lumbar kinematic MRI in the neutral, flexion, and extension positions. Segmental displacement and intervertebral angles were measured in 3 positions using computer analysis software. Modic changes, disc degeneration, disc bulging, spondylolisthesis, angular motion, and translational motion were recorded, and the relationship of MCs to these factors was analyzed using a logistic regression model. To control the influence of disc degeneration on segmental motion, angular and translational motion were analyzed according to mild and severe disc degeneration stages. The motion characteristics and disc degeneration among types of MCs were also evaluated.

RESULTS

Multivariate analysis revealed that age, disc degeneration, angular motion, and translational motion were factors significantly related to MCs. In the severe disc degeneration stage, a significant decrease of angular motion and significant increase of translational motion were found in segments with MCs, indicating that a disorder of the endplate had an additional effect on segmental motion. Disc degeneration increased and angular motion decreased significantly and gradually as the type of MC increased. Translational motion was significantly increased with Type 2 MCs.

CONCLUSIONS

Age, disc degeneration, angular motion, and translational motion were significantly linked to MCs in the lumbar spine. The translational motion of lumbar segments increased with Type 2 MCs, whereas angular motion decreased as the type of MC increased, indicating that Type 2 MCs may have translational instability likely due to degenerative changes. A disorder of the endplates could play an important role in spinal instability.