Visual Evoked Potential Can Predict Deterioration of Visual Function After Direct Clipping of Paraclinoid Aneurysm With Anterior Clinoidectomy.

BACKGROUND: The role of visual evoked potential (VEP) in direct clipping of the paraclinoid internal carotid artery (ICA) aneurysm remains uncertain. OBJECTIVE: To examine whether intraoperative neuromonitoring with VEP can predict deterioration of visual function after direct clipping of the paraclinoid ICA aneurysm with anterior clinoidectomy. METHODS: Among consecutive 274 patients with unruptured cerebral aneurysm, we enrolled 25 patients with paraclinoid ICA aneurysm treated by direct clipping after anterior clinoidectomy with intraoperative neuromonitoring with VEP in this study. We evaluated the visual acuity loss (VAL) and visual field loss (VFL) before surgery, 1 month after surgery, and at the final follow-up. RESULTS: The VAL at 1 month after surgery (VAL1M) and VAL at the final follow-up (Final VAL) were significantly related to the reduction rate of VEP amplitude at the end of surgery (RedEnd%), more than 76.5%, and the maximal reduction rate of VEP amplitude during surgery (MaxRed%), more than 66.7% to 70%. The VFL at 1 month after surgery (VFL1M) and the VFL at the final follow-up (Final VFL) were significantly related to MaxRed% more than 60.7%. CONCLUSION: VAL1M, Final VAL, VFL1M, and Final VFL could be significantly predicted by the value of RedEnd% and MaxRed% in direct clipping of Al-Rodhan group Ia, Ib, and II paraclinoid ICA aneurysms with anterior clinoidectomy.

Spinal endoscopy combined with selective CT myelography for dural closure of the spinal dural defect with superficial siderosis: technical note.

The authors describe a new procedure to detect the tiny dural hole in patients with superficial siderosis (SS) and CSF leakage using a coronary angioscope system for spinal endoscopy and selective CT myelography using a spinal drainage tube. Under fluoroscopy, surgeons inserted the coronary angioscope into the spinal subarachnoid space, similar to the procedure of spinal drainage, and slowly advanced it to the cervical spine. The angioscope clearly showed the small dural hole and injured arachnoid membrane. One week later, the spinal drainage tube was inserted, and the tip of the drainage tube was located just below the level of the dural defect found by the spinal endoscopic examination. This selective CT myelography clarifies the location of the dural defect. During surgery, the small dural hole could be easily located, and it was securely sutured. It is sometimes difficult to detect the actual location of the small dural hole even with thin-slice MRI or dynamic CT myelography in patients with SS. The use of a coronary angioscope for the spinal endoscopy combined with selective CT myelography may provide an effective examination to assess dural closure of the spinal dural defect with SS in cases without obvious dural defects on conventional imaging.

Predictive Factors for the Occurrence of Visual and Ischemic Complications After Open Surgery for Paraclinoid Aneurysms of the Internal Carotid Artery.

OBJECTIVE: To investigate the predictive factors for visual and ischemic complications after open surgery for paraclinoid aneurysms of the internal carotid artery (ICA). MATERIALS AND METHODS: Thirty-eight consecutive patients with unruptured paraclinoid aneurysms of ICA operated on between 2009 and 2013 were included in this study. The male:female ratio was 6:32 and the ages ranged from 33 to 81 (mean: 60 ± 2). Twenty cases were asymptomatic and 18 had ophthalmological symptoms. The sizes of the aneurysms ranged from 2 to 35 mm (mean: 10.6 ± 9 mm). Twenty-three patients were treated by clipping and 15 by trapping with bypass (high-flow bypass in 11, and low-flow in 4). Twenty-four patients underwent removal of the anterior clinoid process. Among them, 8 underwent en bloc anterior clinoidectomy with a high-speed drill, and 16 had piecemeal excision with a microrongeur or ultrasonic bone curette. Intraoperative monitoring was performed using motor-evoked potentials (MEP) and visual-evoked potentials (VEP) in 27 and 15 cases, respectively. RESULTS: Complete obliteration of the aneurysm was achieved in 37 cases (97.4 %). The patency rate of bypass was 100 %. Postoperative worsening of visual acuity, including one case of blindness, was observed in six cases (11 %). Worsening of visual field defects occurred in 14 cases (38 %), but 10 of them were transient. Transient oculomotor nerve palsy occurred in six cases (15 %). Postoperative stroke was detected by diffusion-weighted imaging (DWI) in five cases (13 %), four of which were symptomatic. Statistical analysis showed that piecemeal anterior clinoidectomy was significantly safer than en bloc removal in preserving visual function. Trapping with high-flow bypass had a significantly greater risk of postoperative stroke than direct clipping. CONCLUSIONS: Intraoperative VEP monitoring might be useful for preventing postoperative worsening of visual function. Two-stage treatment with bypass and endovascular trapping might be safer than single-stage trapping alone.

The three-dimensional assessment of dynamic changes of the proximal segments after intraoral vertical ramus osteotomy.

OBJECTIVES: The aim of this study was to assess the positional changes of the proximal segments after intraoral vertical ramus osteotomy (IVRO). METHOD: Fifteen patients underwent IVRO and were followed according to the authors' unique postoperative management regimen. The analyses of the positions and angles of the proximal segments were performed on frontal and lateral cephalograms, which were taken before surgery (T1) and within 3 days (T2), at 4 weeks (T3), and later than 6 months after surgery (T4). The three-dimensional positions of the condylar heads were also assessed by CT images, which were taken before and 1 year after surgery. RESULTS: The proximal segments temporarily swung posteriorly and laterally with a center on the condylar head as a fulcrum point at T2 and T3, compared with T1, and they repositioned at T4. The condylar heads moved inferior approximately 2 mm with lateral rotation one year after surgery, as seen in the CT. DISCUSSION: The condylar heads changed their positions physiologically for newly established jaw movement after IVRO with the authors' post-operative management regimen because the post-operative skeletal stability and the jaw function were good and stable using this method.

Application of a real-time three-dimensional navigation system to various oral and maxillofacial surgical procedures.

The aim of this study was to confirm the effectiveness of a real-time three-dimensional navigation system for use during various oral and maxillofacial surgeries. Five surgeries were performed with this real-time three-dimensional navigation system. For mandibular surgery, patients wore acrylic surgical splints when they underwent computed tomography examinations and the operation to maintain the mandibular position. The incidence of complications during and after surgery was assessed. No connection with the nasal cavity or maxillary sinus was observed at the maxilla during the operation. The inferior alveolar nerve was not injured directly, and any paresthesia around the lower lip and mental region had disappeared within several days after the surgery. In both maxillary and mandibular cases, there was no abnormal hemorrhage during or after the operation. Real-time three-dimensional computer-navigated surgery allows minimally invasive, safe procedures to be performed with precision. It results in minimal complications and early recovery.

Thin-film electroencephalographic electrodes using multi-walled carbon nanotubes are effective for neurosurgery.

BACKGROUND: Intraoperative morphological and functional monitoring is essential for safe neurosurgery. Functional monitoring is based on electroencephalography (EEG), which uses silver electrodes. However, these electrodes generate metal artifacts as silver blocks X-rays, creating white radial lines on computed tomography (CT) images during surgery. Thick electrodes interfere with surgical procedures. Thus, thinner and lighter electrodes are ideal for intraoperative use. METHODS: The authors developed thin brain electrodes using carbon nanotubes that were formed into thin sheets and connected to electrical wires. RESULTS: The nanotube sheets were soft and fitted the curve of the head very well. When attached to the head using paste, the impedance of the newly developed electrodes was 5 kΩ or lower, which was similar to that of conventional metal electrodes. These electrodes can be used in combination with intraoperative CT, magnetic resonance imaging (MRI), or cerebral angiography. Somatosensory-evoked potentials, auditory brainstem responses, and visually evoked potentials were clearly identified in ten volunteers. The electrodes, without any artifacts that distort images, did not interfere with X-rays, CT, or MR images. They also did not cause skin damage. CONCLUSIONS: Carbon nanotube electrodes may be ideal for neurosurgery.

Pathomechanisms of sciatica in lumbar disc herniation: effect of periradicular adhesive tissue on electrophysiological values by an intraoperative straight leg raising test.

STUDY DESIGN: This study is aimed to investigate the changes of nerve root functions during the straight leg raising (SLR) test in vivo. OBJECTIVE: To investigate the relationship between nerve root movement and the electrophysiological values during an intraoperative SLR test. SUMMARY OF BACKGROUND DATA: The SLR test is one of the most significant signs for making a clinical diagnosis of lumbar disc herniation. A recent study showed that intraradicular blood flow apparently decreased during the SLR test in patients with disc herniation. METHODS: The study included 32 patients who underwent microdiscectomy. During the surgery, the nerve root motion affected by the hernia was observed during the SLR test. The patients' legs were allowed to hang down to the angle at which sciatica had occurred and the change of nerve root action potentials was measured. After removal of the hernia, a similar procedure was repeated. The periradicular specimens collected during surgery were examined by light and electron microscope. RESULTS: In all patients intraoperative microscopy revealed that the hernia was adherent to the dura mater of the nerve roots. During the SLR test, the limitation of nerve root movement occurred by periradicular adhesive tissue and amplitude of action potential showed a sharp decrease at the angle that produced sciatica. After removal of the hernia, all the patients showed smooth gliding of the nerve roots during the test, and there was no marked decrease of amplitude. Our data suggest that temporary ischemic changes in the nerve root cause transient conduction disturbances. Pathologic examination showed that the periradicular tissue consisted of the granulation with vascularization and many inflammatory cell infiltrations. CONCLUSION: The presence of periradicular fibrosis will compound the nerve root pain by fixing the nerve in one position, thereby increasing the susceptibility of the nerve root to tension or compression.

Intraneural blood flow analysis during an intraoperative Phalen's test in carpal tunnel syndrome.

Phalen's test has been one of the most significant of clinical signs when making a clinical diagnosis of idiopathic carpal tunnel syndrome (CTS). However, it is unknown whether intraneural blood flow changes during Phalen's test in patients with CTS. In this study, an intraoperative Phalen's test was conducted in patients with CTS to observe the changes in intraneural blood flow using a laser Doppler flow meter. During Phalen's test, intraneural blood flow showed a sharp decrease, which lasted for 1 min. Intraneural blood flow decreased by 56.7%-100% (average, 78.0%) in the median nerve relative to the blood flow before the test. At 1 min after completing the test, intraneural blood flow returned to the baseline value. After carpal tunnel release, there was no marked decrease in intraneural blood flow. This study demonstrated that the blood flow in the median nerve is reduced when Phalen's test is performed in vivo.