Saiko Watanabe

Microvascular decompression for hemifacial spasm: how can we protect auditory function?

Abstract Objective. The nerve function of the VIIIth nerve is at risk during microvascular decompression (MVD) for hemifacial spasm (HFS). Intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) can be useful in decreasing the danger of hearing loss. This study assessed the intraoperative BAEP findings related to the surgical process to clarify the optimum maneuvers of MVD surgery to avoid hearing impairment. Methods. Hundred consecutive patients undergoing MVD for HFS with intraoperative BAEP monitoring were retrospectively reviewed. Patients were classified into four groups based on the greatest intraoperative latency prolongation and amplitude reduction of wave V of BAEP. Postoperative hearing function and surgical procedures including use of the brain retractor, preservation of arachnoid membrane along the VIIIth nerve, and duration of microscopic manipulation were analyzed in relation to the BAEP findings. Results. Three patients complained of hearing loss after the surgery, but two had complete recovery and only one suffered permanent moderate hearing impairment. Longer duration of microscopic manipulation and greater use of the brain retractor tended to have negative effects on the BAEP findings, whereas preservation of arachnoid membrane along the VIIIth nerve had a positive effect. Statistical analysis showed significant difference in preservation of arachnoid membrane along the VIIIth nerve in Groups 2 and 4 (p = 0.013). Conclusion. Stretching of the VIIIth nerve should be avoided to prevent postoperative hearing impairment. Adequate exposure of the lower cranial nerve roots and lateral medulla oblongata from the caudal side without using the brain retractor gives enough space for decompression with minimum stretching of the VIIIth nerve. Maximum preservation of the arachnoid membrane along the VIIIth nerve and shortening of the duration of microscopic manipulation may help in avoiding postoperative hearing impairment.

Lower cranial nerve palsy after the infrafloccular approach in microvascular decompression for hemifacial spasm

Background: The infrafloccular approach was introduced as a variation in microvascular decompression (MVD) for hemifacial spasm. However, the rate of postoperative lower cranial nerve (CN) palsy can be high. This study investigated the surgical factors in relation to the occurrence of postoperative lower CN palsy. Methods: The case records of 103 patients who underwent MVD were reviewed. Dissection around the lower CNs to approach the root exit zone of CN VII was divided into two steps – incision of the rhomboid lip at the root of the lower CNs and separation of CN IX and flocculus/choroid plexus. The correlations of these steps and other characteristics to the occurrence of lower CN palsy were analyzed. Results: Ten of the 103 patients suffered from postoperative transient lower CN palsy. The rhomboid lip was incised in 30 cases (29.1%), separation of CN IX and flocculus or choroid plexus was necessary in 24 cases (23.3%), and both steps were required in 7 cases (6.8%). The steps showed no correlation with postoperative lower CN palsy. Posterior inferior cerebellar artery (PICA) as the offending vessel was significantly correlated with postoperative lower CN palsy (P < 0.05). Conclusions: Our study showed that the offending PICA was the only significant factor for postoperative lower CN palsy. Therefore, correct dissection around the lower CNs, particularly for complicated PICA, is necessary to reduce the risk of postoperative lower CN palsy.

Trigeminal neuralgia caused by a trigeminocerebellar artery

This 31-year-old woman presented with typical right trigeminal neuralgia caused by a trigeminocerebellar artery, manifesting as pain uncontrollable with medical treatment. Preoperative neuroimaging studies demonstrated that the offending artery had almost encircled the right trigeminal nerve. This finding was confirmed intraoperatively, and decompression was completed. The neuralgia resolved after the surgery; the patient had slight transient hypesthesia, which fully resolved within the 1st month after surgery. The neuroimaging and intraoperative findings showed that the offending artery directly branched from the upper part of the basilar artery and, after encircling and supplying tiny branches to the nerve root, maintained its diameter and coursed toward the rostral direction of the cerebellum, which indicated that the artery supplied both the trigeminal nerve and the cerebellum. The offending artery was identified as the trigeminocerebellar artery. This case of trigeminal neuralgia caused by a trigeminocerebellar artery indicates that this variant is important for a better understanding of the vasculature of the trigeminal nerve root.

Safety of microvascular decompression for elderly patients with trigeminal neuralgia.

OBJECTIVE The present study compared the safety and efficacy of microvascular decompression (MVD) in groups of elderly patients and non-elderly patients with medically refractory trigeminal neuralgia (TN) and collected detailed perioperative data. METHODS Retrospective analysis of clinical data was performed in 99 patients who underwent MVD from May 2012 to June 2015. The outcome data from 27 MVD operations for 27 patients aged 70-80 years (mean 74.6 years) were compared with 72 MVD operations with 72 patients aged 25-69 years (mean 55.7 years). Preoperative comorbidities were recorded and postoperative worsening comorbidities and non-neurological complications were evaluated at discharge. Efficacy of the surgery and neurological complications were evaluated in July 2015. RESULTS No decrease in activity of daily living was found in any patient. Complete pain relief without medication was achieved in 77.8% and partial pain relief in 14.8% in the elderly group, and 83.3% and 9.7%, respectively, in the non-elderly group (p=0.750). Permanent neurological complication was not observed in the elderly group, whereas Vth nerve and VIIIth nerve complications were observed in the non-elderly group. Rates of preoperative multiple comorbidities and of cardiovascular comorbidity were significantly higher in the elderly group (p<0.01). Worsening comorbidity and new pathology at discharge were mainly hypertension in both groups, but glaucoma attack and asthma attack were observed in the elderly group. All pathologies were successfully managed. CONCLUSIONS MVD for elderly patients with TN can be achieved safely with careful perioperative management. Information of comorbidity should be shared with all staff involved in the treatment, who should work as a team to avoid worsening comorbidity. The possibility of unpredictable events in the elderly patients should always be considered.

Acute Glaucoma Attack Following Microvascular Decompression Surgery for Trigeminal Neuralgia

Microvascular decompression (MVD) is widely accepted as an effective surgical method to treat trigeminal neuralgia (TN), but the risks of morbidity and mortality must be considered. We experienced a case of acute angle-closure glaucoma attack following MVD for TN in an elderly patient, considered to be caused by lateral positioning during and after the surgery. A 79-year-old female underwent MVD for right TN in the left lateral decubitus position, and TN disappeared after the surgery. Postoperatively, the patient tended to maintain the left lateral decubitus position to prevent wound contact with the pillow, even after ambulation. Two days after the surgery, she complained of persistent left ocular pain with visual disturbance. The left pupil was dilated with only light perception, and the intraocular pressure (IOP) was 44 mmHg. Acute angle-closure glaucoma attack was diagnosed. After drip infusion of mannitol, emergent laser iridotomy was performed. The corrected visual acuity recovered with normalization of IOP (14 mmHg). The subsequent clinical course was uneventful and she was discharged from our hospital. The left lateral positioning during and after the surgery was considered to have contributed to increase IOP of the eye on the dependent side, which resulted in acute angle-closure glaucoma attack. The potential pathology is difficult to assess preoperatively, but patient management should always consider the increased possibility of this condition with age.

Fibrin glue injection into the hematoma cavity for refractory chronic subdural hematoma: A case report

Background: Repeat burr hole irrigation and drainage has been effective in most cases of recurrent chronic subdural hematoma (CSDH), however, refractory cases require further procedures or other interventions. Case Description: An 85-year-old male presented with left CSDH, which recurred five times. The hematoma was irrigated and drained through a left frontal burr hole during the first to third surgery and through a left parietal burr hole during the fourth and fifth surgery. The hematoma had no septation and was well-evacuated during each surgery. Antiplatelet therapy for preventing ischemic heart disease was stopped after the second surgery, the hematoma cavity was irrigated with artificial cerebrospinal fluid at the third surgery, and the direction of the drainage tube was changed to reduce the postoperative subdural air collection at the fourth surgery. However, none of these interventions was effective. He was successfully treated by fibrin glue injection into the hematoma cavity after the fifth surgery. Conclusion: This procedure may be effective for refractory CSDH in elderly patients.