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Keisuke Takai and Makoto Taniguchi

OBJECTIVE

Dorsal root entry zone (DREZ) lesioning has been the most effective surgical treatment for the relief of intractable pain due to root avulsion injury, but residual pain and a decrease in pain relief in the follow-up period have been reported in 23%–70% of patients. Based on pain topography in the most recent studies on neuropathic pain, the authors modified the conventional DREZ lesioning procedure to improve clinical outcomes. The presumed rationale for this procedure is to eliminate the spontaneous discharges of neurons in the superficial spinal dorsal horn as well as wide dynamic range neurons in the deep spinal dorsal horn.

METHODS

Ten patients with avulsion-related pain underwent surgery between 2011 and 2015. The surgical procedure was described and postoperative pain relief was assessed as follows: excellent (residual pain never exceeded 3 on the visual analog scale [VAS] without medication), good (residual pain never exceeded 5 on the VAS with medication), and poor (residual pain was greater than 5 with medication). Specific perioperative complications were assessed.

RESULTS

The aim of this surgical procedure was to destroy the deeper layers of the posterior horn of spinal gray matter, which was in contrast to the procedures of Nashold and Sindou, which were to destroy the superficial layers. All patients achieved excellent (n = 7, pain relief without medication) or good (n = 3, pain relief with medication) pain relief postoperatively, and the recurrence of pain was not reported in any patients (median 29 months after surgery, range 12–64 months). Nine patients (90%) achieved complete pain relief (a score of 0 or 1 on the VAS) with or without medication. No surgical site complications such as infection or CSF leakage were noted. No motor deficit was observed in any patient. A sensory deficit was observed in 2 patients and disappeared within 1 month in 1 patient. New pain at the adjacent level of DREZ lesioning was observed in 3 patients and disappeared within 1 month in 2 patients. In the other patient, new pain persisted and required analgesics.

CONCLUSIONS

These preliminary results demonstrated that total and persistent global pain relief was achieved with the modified DREZ lesioning procedure in 90% of patients without major neurological deficits. The clinical improvements achieved by this modified surgical procedure support the hypothesis that not only the superficial layers, but also deeper layers of the spinal dorsal horn are associated with intractable pain due to root avulsion injury.

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Keisuke Takai and Makoto Taniguchi

Object

Spinal arteriovenous malformations (AVMs) are classified into types according to anatomical characteristics: dural arteriovenous fistulas (AVFs), intramedullary AVMs, perimedullary AVFs, and extradural AVFs. Spinal extradural AVFs are much rarer than other types of spinal AVMs, and the available literature on this clinical entity has been based only on case reports or small case series. To investigate the clinical characteristics of patients with spinal extradural AVFs, the authors systematically reviewed the associated literature in the MRI era.

Methods

The PubMed database was searched for all relevant English-language case reports and case series published from 1990 to 2011. The clinical differences between Type A with and Type B without intradural venous drainage were statistically compared, especially regarding clinical features and angiographic and MRI findings.

Results

Forty-five cases of spinal extradural AVFs were found. Type A spinal extradural AVFs were diagnosed in patients with a significantly older age (mean 63.5 years) as compared with Type B AVFs (mean 34.3 years, p < 0.0001). Most cases of Type A spinal extradural AVFs exhibited a diffuse high signal intensity of the spinal cord on T2-weighted MR images and no mass effect (p < 0.0001), and they commonly occurred in the thoracolumbar and lumbar regions (p < 0.0001). On the other hand, cases of Type B lesions exhibited a normal signal intensity of the cord with severe mass effect due to an enlarged extradural venous plexus, and they commonly occurred in the cervical and upper thoracic regions (p < 0.0001), frequently in patients with neurofibromatosis Type 1 (p = 0.049). Because Type B AVFs consisted of high-flow, multiple complex anastomoses between arteries and the epidural venous plexus, patients with these lesions tended to undergo multisession treatments, and the rate of partial AVF occlusion was significantly higher than for Type A AVFs (p = 0.018), although there was no difference in symptom outcomes between the 2 groups.

Conclusions

To the best of the authors' knowledge, a comparative analysis of the clinical differences in patients with extradural AVFs with or without intradural venous drainage has yet to be described in the literature. They concluded that in the diagnosis of spinal extradural AVF, evaluation of intradural venous drainage is important because the cause of myelopathy determines the treatment goals.

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Keisuke Takai, Takashi Komori and Makoto Taniguchi

OBJECT

The microvascular anatomy of spinal dural arteriovenous fistulas (AVFs), especially the relationships of the vessels with the dura mater, has yet to be angiographically demonstrated in detail and proven histologically.

METHODS

From January 2012 through April 2014, a total of 7 patients with spinal dural AVFs in the thoracic region underwent open microsurgical obliteration at Tokyo Metropolitan Neurological Hospital. The microvascular anatomy of spinal dural AVFs was comprehensively assessed by using advanced microangiography, including 3D computer graphics and intraoperative indocyanine green video angiography, and by histological findings.

RESULTS

The 2 microangiography techniques revealed the spatial course and in vivo blood flow of the meningeal vessels and their relationships with the dura mater in sufficient detail. The meningeal branch of the intercostal artery split into multiple meningeal vessels on the outer dural surface adjacent to the root sleeve. After crossing the dura mater to the inner dural surface, these vessels gathered and joined a single intradural draining vessel. On the inner dural surface, the single draining vessel was fed by the surrounding multiple meningeal vessels, which appeared to be caput medusae.

Histological findings revealed that the structure of the meningeal branch of the intercostal artery corresponded to that of a normal artery. The structure of intradural draining vessels corresponded to that of a vein modified by retrograde arterial inflow. On the inner dural surface, more than 1 meningeal artery gathered and joined with the proximal radiculomedullary vein.

CONCLUSIONS

Spinal dural AVFs are located on the inner dural surface, where multiple direct AV connections between more than 1 meningeal feeding artery and a single proximal radiculomedullary vein occur at the site where the vein connects to the dura mater.

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Hiroki Yoshida, Keisuke Takai and Makoto Taniguchi

Object

The purpose of this study was to describe significant CT myelography findings for determination of the leak site and outcome of targeted epidural blood patch (EBP) in patients with spontaneous CSF leaks.

Methods

During 2005–2013, spontaneous CSF leaks were diagnosed for 12 patients with orthostatic headaches. The patients received targeted EBP on the basis of CT myelography assessments.

Results

Computed tomography myelograms revealed ventral extradural collection of contrast medium distributed over multiple spinal levels (average 16 levels). Intraforaminal contrast medium extravasations were observed at multiple spinal levels (average 8.2 levels). For 8 (67%) of 12 patients, spinal lesions were noted around the thecal sac and included calcified discs with osteophytes, an ossified posterior longitudinal ligament, and an ossified yellow ligament; lesions were mostly located ventral to the thecal sac and were in close contact with the dura mater. The levels of these spinal lesions were considered potential leak sites and were targeted for EBP. For the remaining 4 patients who did not have definite spinal lesions around the thecal sac, leak site determination was based primarily on the contrast gradient hypothesis. The authors hypothesized that the concentration of extradural contrast medium would be the greatest and the same as that of intradural contrast medium at the leak site but that it would decrease with increased distance from the leak site according to the contrast gradient.

Epidural blood patch was placed at the level of spinal lesions and/or of the greatest and same concentration of contrast medium between the intradural and extradural spaces. For 10 of the 12 patients, the orthostatic headaches decreased significantly within a week of EBP and disappeared within a month. For the remaining 2 patients, headaches persisted and medical treatment was required for several months. For 3 patients, thick chronic subdural hematomas caused severe headaches and/or disturbed consciousness because of the mass effect of the hematomas, which were removed by bur hole drainage surgery. For 1 patient, bur hole drainage before EBP on the day of admission to hospital resulted in subdural tension pneumocephalus. The patient's headache immediately disappeared after EBP, and the hematoma did not recur. The other 2 patients underwent EBP followed by bur hole drainage, which resulted in improvements and disappearance of the hematomas. Over the follow-up period (mean 39 months), no CSF leaks or chronic subdural hematomas had recurred in any patient after EBP; by the final follow-up visit, all patients had returned to their jobs.

Conclusions

The most significant finding of this study was that spinal ventral calcified or ossified lesions, which may be associated with a dural tear, were present in approximately 70% of patients. Targeted EBP to these lesions resulted in good outcomes.

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Hirotaka Ito, Keisuke Takai and Makoto Taniguchi

Object

Hirayama disease, juvenile muscular atrophy of the distal upper extremity, is a rare type of cervical flexion segmental myelopathy and its etiology is still being debated. Two theories have been proposed: a “contact pressure” theory and “tight dural canal in flexion” theory. Previously reported treatments, including conservative neck collar therapy and surgical spinal fusion, used fixation of the cervical spine with the aim of avoiding contact pressure between the cord and anterior structures. On the other hand, treatment by duraplasty without spinal fusion has also been used, which aims at decompressing a tight dural canal in flexion by preventing abnormal forward displacement of the posterior dura mater without restricting cervical motion in young patients.

The authors developed a new surgical approach for treating a tight dural canal in flexion in patients with Hirayama disease: cervical duraplasty with tenting sutures via laminoplasty without spinal fusion. With this treatment they aimed to both decompress the spinal cord and preserve as much cervical motion as possible. The purpose of this study was to assess the clinical outcomes of patients who underwent this new surgical procedure and to investigate the etiology of Hirayama disease.

Methods

Six male patients (age range 17–23 years) with Hirayama disease underwent surgery between 2006 and 2012. The pre- and postoperative anteroposterior diameters of the dural canal in the flexed neck position, grip strength of the bilateral upper extremities, cervical alignment (C2–7), and cervical local flexion range of motion were compared. The presence or absence of surgical complications was assessed. To investigate the comparison group of Hirayama disease treated with spinal decompression, the PubMed database was searched for all relevant Englishlanguage case reports and series published between 1990 and 2013.

Results

The postoperative anteroposterior diameters of the dural canal were significantly expanded in the flexed neck position (7.2 ± 2.2 mm preoperatively vs 9.8 ± 1.7 mm postoperatively, p = 0.001). Grip strength of the upper extremities significantly improved bilaterally (20 ± 14 kg preoperatively vs 26 ± 15 kg postoperatively, p = 0.001). No significant difference was observed between pre- and postoperative cervical alignment in the neutral neck position (7.7° ± 8.1° preoperatively vs 9.0° ± 7.7° postoperatively, p = 0.74) or the cervical local flexion angle in the flexed neck position at the corresponding level of laminoplasty (16.6° ± 5.1° preoperatively vs 15.0° ± 9.4° postoperatively, p = 0.8). No surgical complications were noted, except for transient CSF leakage, which was resolved after lumbar drainage. The systematic review identified 37 cases from 7 reports: 26 with spinal fusion only, 5 with duraplasty without fusion, and 6 with combined duraplasty and fusion. In the largest series, in which 12 cases were treated with anterior fusion, cervical alignment was maintained, but local flexion motion was significantly decreased as a result of fixation. Although significant improvements in or stabilization of grip strength occurred in all 7 reported studies regardless of decompression procedures, one major delayed surgical complication was noted in a patient treated with anterior fusion. The patient developed severe kyphotic changes, which required reconstruction surgeries.

Conclusions

Cervical duraplasty with tenting sutures via laminoplasty prevented abnormal forward displacement of the posterior dura mater while preserving normal anterior structures and flexion motion of the cervical spine without major surgical complications. The clinical improvements achieved by the authors' method support evidence that a tight dural canal in flexion largely contributes to segmental myelopathy in patients with Hirayama disease.

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Tetsuhiro Nishihara, Akira Teraoka, Akio Morita, Keisuke Ueki, Keisuke Takai and Takaaki Kirino

✓ The authors advocate the use of a transparent sheath for guiding an endoscope, a simple and unique tool for endoscopic surgery, and describe preliminary results of its application in the evacuation of hypertensive intracerebral hematomas. This sheath is a 10-cm-long tube made of clear acrylic plastic, which greatly improves visualization of the surgical field through a 2.7-mm nonangled endoscope inserted within. Between April 1997 and December 1998, the authors performed endoscopic evacuation of intracerebral hematomas by using this sheath inserted into the patients' heads through a burr hole. In nine consecutive cases in which the hematoma was larger than 40 ml in volume, nearly complete evacuation (86–100%) of the lesion was achieved without complication. Excellent visualization of the border between the brain parenchyma and the hematoma facilitated accurate intraoperative orientation, and also allowed easy identification of the bleeding point. Thus, this combination of sheath and endoscope achieves both minimal invasiveness and the maximum extent of hematoma removal with secure hemostasis. This tool will reduce the inherent disadvantage of endoscopic procedures and may expand their application in other areas of neurosurgical management.

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Hiroki Hongo, Keisuke Takai, Takashi Komori and Makoto Taniguchi

OBJECTIVE

The intraoperative differentiation of ependymomas from astrocytomas is important because neurosurgical strategies differ between these two tumor groups. Previous studies have reported that the diagnostic accuracy of intraoperative frozen sections of intracranial central nervous system (CNS) tumors is higher than 83%–97%, whereas that for spinal intramedullary tumors remains unknown. Herein, authors tested the hypothesis that intraoperative frozen-section diagnosis is the gold standard for a differential diagnosis of intramedullary spinal cord tumors.

METHODS

The clinical characteristics, intraoperative histological diagnosis from frozen sections, extent of tumor resection, progression-free survival (PFS), and overall survival (OS) of 49 cases of intramedullary spinal cord ependymomas (n = 32) and astrocytomas (n = 17) were retrospectively evaluated.

RESULTS

The frozen-section diagnosis and final diagnosis with permanent sections agreed in 23 (72%) of 32 cases of ependymoma. Of the 9 cases of ependymoma in which the frozen-section diagnosis disagreed with the final diagnosis, 4 were incorrectly diagnosed as astrocytoma and the other 5 cases had a nonspecific diagnosis, such as glioma. Nonetheless, gross-total resection was achieved in 6 of these 9 cases given the presence of a dissection plane. The frozen-section diagnosis and final diagnosis agreed in 12 (71%) of 17 cases of astrocytoma. Of the 5 cases of astrocytoma in which the frozen-section diagnosis disagreed with the final diagnosis, 1 was incorrectly diagnosed as ependymoma and the other 4 had a nonspecific diagnosis. Gross-total resection was achieved in only 1 of these 5 cases.

A relationship between the size of tumor specimens and the diagnostic accuracy of frozen sections was not observed. Ependymal rosettes and perivascular pseudorosettes were observed in 30% and 57% of ependymomas, respectively, but were absent in astrocytomas.

Progression-free survival and OS were both significantly longer in cases of ependymoma than in cases of astrocytoma (p < 0.001). Gross-total resection was achieved in 69% of ependymomas and was associated with longer PFS (p = 0.041). In the astrocytoma group, gross-total resection was achieved in only 12% and there was no relationship between extent of resection and OS. Tumor grades tended to correlate with OS in astrocytomas (p = 0.079).

CONCLUSIONS

The diagnostic accuracy of intraoperative frozen sections was lower for intramedullary spinal cord ependymomas and astrocytomas in the present study than that for intracranial CNS tumors reported on in the literature. Surgical strategies need to be selected based on multiple factors, such as clinical characteristics, preoperative imaging, frozen-section diagnosis, and intraoperative findings of the tumor plane.

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Keisuke Takai, Takashi Komori, Manabu Niimura and Makoto Taniguchi

In most patients with superficial siderosis of the CNS, the exact source of bleeding remains unknown because of a lack of objective surgical data. The authors herein describe the case of a 58-year-old man with superficial siderosis of the CNS. The patient also had spinal CSF leakage due to a spinal dural defect. Repair surgery for the dural defect was performed using posterior laminoplasty with a transdural approach without spinal fixation. During repair surgery, the bleeding source was found to be the epidural vein around the defect. The intraoperative and histological results of the present case suggest that epidural veins exposed to CSF represent a chronic bleeding source in patients with superficial siderosis of the CNS complicated by CSF leakage. Dural repair surgery may result in discontinuation of the CSF leaks, resolution of the epidural CSF collection, and cessation of chronic epidural bleeding.

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Keisuke Takai, Hiroki Kurita, Takayuki Hara, Kensuke Kawai and Makoto Taniguchi

OBJECTIVE

The microvascular anatomy of spinal perimedullary arteriovenous fistulas (AVFs) is more complicated than that of dural AVFs, and occlusion rates of AVF after open microsurgery or endovascular embolization are lower in patients with perimedullary AVFs (29%–70%) than they are in those with dural AVF (97%–98%). Reports of intraoperative blood flow assessment using indocyanine green (ICG) video angiography in spinal arteriovenous lesions have mostly been for spinal dural AVFs. No detailed reports on spinal perimedullary AVFs are available.

METHODS

Participants were 11 patients with spinal perimedullary AVFs (Type IVa in 5 patients, Type VIb in 4, and Type IVc in 2). Intraoperative ICG video angiography was assessed by measuring the number of cases in which this modality was judged essential by the surgeon to correctly occlude the fistula.

RESULTS

In all patients, arterial feeders were identified and intravenous ICG video angiography was performed before and after blocking the feeders. In one patient, selective intraarterial ICG video angiography was also performed. The findings provided by ICG video angiography significantly changed the surgical procedure in 4 of 11 patients (36%). Postoperatively, complete occlusion of the AVF was achieved in 10 of the 11 patients (91%).

CONCLUSIONS

Intraoperative ICG video angiography can have a significant impact on deciding surgical strategy in the microsurgical treatment of spinal perimedullary AVF.