佐藤 信

Endoscopic third ventriculostomy (ETV) is a safe treatment option for chronic obstructive hydrocephalus. However, we encountered a case of chronic subdural hematoma (CSDH) with bilateral large hematoma volumes after ETV for chronic obstructive hydrocephalus. We herein report a rare complication of ETV. The patient was a 53-year-old woman who had been diagnosed with asymptomatic ventricular enlargement with aqueductal stenosis 5 years previously. However, over the course of 5 years, her gait and cognitive function gradually declined. ETV was administered to relieve symptoms. Head Magnetic resonance imaging performed 1 week after ETV indicated bilateral subdural hygroma. Three weeks after ETV, she presented with headache and left incomplete paralysis, and head Computed tomography (CT) demonstrated bilateral CSDH with a large volume hematoma. Burr-hole evacuation and drainage of the bilateral CSDH were performed, after which the symptoms resolved. However, 7 weeks after ETV, she again presented with headache and incomplete right paralysis, and CT revealed bilateral CSDH re-enlargement. After the second burr-hole evacuation and drainage of bilateral CSDH, her symptoms resolved. The bilateral CSDH continued to shrink following the second hematoma evacuation surgery and completely disappeared on CT scan performed 3 months after ETV. Ventricular enlargement due to chronic obstructive hydrocephalus stretches the brain mantle for several years. This long-term stretching may have diminished the brain compliance and led to the development, growth, and recurrence of CSDH. In ETV for chronic obstructive hydrocephalus, surgeons should consider the risk of postoperative CSDH with a high hematoma volume and tendency to recur.

Insertion of a deep brain stimulating electrode is a commonly performed procedure. Burr hole caps play an important role in this procedure by immobilizing this electrode; however, burr hole caps could form scalp bumps, which can create further complications. The dual-floor burr hole technique could prevent the formation of scalp bumps. This technique has previously been used with older versions of burr hole caps and has proved to be successful. In recent years, modern burr hole caps with an internal electrode locking mechanism have become the mainstay for this procedure. However, modern burr hole caps differ considerably in diameter and shape from older burr hole caps. In the present study, a dual-floor burr hole technique was performed using modern burr hole caps. To accommodate the increase in diameters and changes in the shape of modern burr hole caps, a perforator with a 30-mm diameter was used for shaving the bone, and the bone shaving depth was altered. This surgical technique was applied to 23 consecutive deep brain stimulation surgeries without complications and was thus positively optimized for modern burr hole caps.

Stereotactic neurosurgery is an established technique, but it has several limitations. In frame-based stereotaxy using a stereotactic frame, frame setting errors may decrease the accuracy of the procedure. Frameless stereotaxy using neuronavigation requires surgeons to shift their view from the surgical field to the navigation display and to advance the needle while assuming a physically uncomfortable position. To overcome these limitations, several researchers have applied augmented reality in stereotactic neurosurgery. Augmented reality enables surgeons to visualize the information regarding the target and preplanned trajectory superimposed over the actual surgical field. In frame-based stereotaxy, a researcher applies tablet computer-based augmented reality to check for the setting errors of the stereotactic frame, thereby improving the safety of the procedure. Several researchers have reported performing frameless stereotaxy guided by head-mounted-display-based augmented reality that enables surgeons to advance the needle at a more natural posture. These studies have shown that augmented reality can address the limitations of stereotactic neurosurgery. Conversely, they have also revealed the limited accuracy of current augmented reality systems for small targets, which indicates that further development of augmented reality systems is needed.

BACKGROUND: The delivery of adeno-associated virus (AAV) vectors via the cerebrospinal fluid (CSF) has emerged as a valuable method for widespread transduction in the central nervous system. Although infusion into the cerebral ventricles is a common protocol in preclinical studies of small animals, the cisterna magna has been recognized as an alternative target for clinical studies because it can be reached in a less invasive manner using an intrathecal catheter via the subarachnoid space from a lumbar puncture. METHODS: We evaluated the early distribution of fluorine-18-labeled AAV9 vectors infused into the lateral ventricle or cisterna magna of four non-human primates using positron emission tomography. The expression of the green fluorescent protein was immunohistochemically determined. RESULTS: In both approaches, the labeled vectors diffused into the broad arachnoid space around the brain stem and cervical spinal cord within 30 min. Both infusion routes efficiently transduced neurons in the cervical spinal cord. CONCLUSIONS: For gene therapy that primarily targets the cervical spinal cord and brainstem, such as amyotrophic lateral sclerosis, cisterna magna infusion would be a feasible and effective administration method.

To date, several researchers have introduced augmented reality navigation (ARN) into neurological surgery. While its application in brain tumor surgery seems promising, reports on its utility have been limited, thus warranting further evaluation. To clarify the stages and approaches in which ARN is useful and assess the effect of presurgical discussion with surgeons, we assessed usefulness using a hand-held ARN system we had developed, which displays three-dimensional (3D) virtual structures overlaid on a real-time image of the surgical field via a tablet PC monitor. The system was tested in 20 patients undergoing various procedures, with the first 10 consecutive cases being unselected and the following 10 cases being selected, for whom 3D models were prepared per the surgeons' request. Thereafter, the surgeons ranked its usefulness during each stage of surgery. Consequently, case selection and presurgical discussions with surgeons considerably improved the usefulness, with the "useful" gradings improving from 50% to 88% across all surgical stages. Accordingly, usefulness improved from 50% to 90%, 67% to 100%, and 40% to 80% during the skin incision and craniotomy, dura incision, and intradural procedure stages, respectively. ARN was useful for superficial tumor resection, but less so for deep-seated tumor resection, except when using the transcortical and interhemispheric approaches. In conclusion, a tablet-type ARN can be useful during skin incisions, craniotomy and dura incisions, superficial tumor resections, and transcortical and interhemispheric approaches for deep-seated tumors. Case selection and presurgical discussions with surgeons were essential for the efficacy of ARN.