Awake craniotomy for auditory brainstem implant in patients with neurofibromatosis type 2:Four case reports

BACKGROUND The auditory brainstem implant(ABI)is a significant treatment to restore hearing sensations for neurofibromatosis type 2(NF2)patients.However,there is no ideal method in assisting the placement of ABIs.In this case series,intraoperative cochlear nucleus mapping was performed in awake craniotomy to help guide the placement of the electrode array.CASE SUMMARY We applied the asleep-awake-asleep technique for awake craniotomy and hearing test via the retrosigmoid approach for acoustic neuroma resections and ABIs,using mechanical ventilation with a laryngeal mask during the asleep phases,utilizing a ropivacaine-based regional anesthesia,and sevoflurane combined with propofol/remifentanil as the sedative/analgesic agents in four NF2 patients.ABI electrode arrays were placed in the awake phase with successful intraoperative hearing tests in three patients.There was one uncooperative patient whose awake hearing test needed to be aborted.In all cases,tumor resection and ABI were performed safely.Satisfactory electrode effectiveness was achieved in awake ABI placement.CONCLUSION This case series suggests that awake craniotomy with an intraoperative hearing test for ABI placement is safe and well tolerated.Awake craniotomy is beneficial for improving the accuracy of ABI electrode placement and meanwhile reduces non-auditory side effects.

Two Cases of Spinal Tanycytic Ependymoma Associated with Neurofibromatosis Type 2

INTRODUCTION Tanycytic ependymoma is a rare subtype of the World Health Organization Grade il ependymoma most commonly found in the cervical and thoracic segments of the spinal cord. Spinal tumors in neurofibromatosis type 2 （NF-2） can be intramedullary, extramedullary, or associated with the nerve roots, and there may be multiple tumors at multiple locations in the spine.

Isolated colonic neurofibroma, a rare tumor: A case report and review of literature

BACKGROUND Neurofibromas are tumors comprised of peripheral nerve sheath and connective tissue components.They can occur sporadically or as part of familial syndromes such as neurofibromatosis type 1.Isolated colonic neurofibroma without systemic manifestations is a rarely reported clinical entity.Here we present a case of a 51 years old male with an isolated colonic neurofibroma seen on a screening colonoscopy.CASE SUMMARY Fifty-one years old male who was otherwise healthy without a significant family history of cancer underwent a screening colonoscopy and was found have a 2.3 cm×1.4 cm lesion in the colon.Tissue biopsy revealed a spindle cell tumor.Magnetic resonance imaging of the pelvis was negative for adenopathy.He underwent an endoscopic ultrasound that showed an ill-defined avascular lesion of mixed echogenicity measuring 2.8 cm×15.2 cm in the submucosa with no communication with muscularis mucosa or propria.Immunohistochemistry staining of the tumor was strongly positive for S100,with rare penetrating axons deep within the tumor.Tumor cells were negative for c-kit and desmin and had low Ki-67 index.These findings were consistent with a solitary colonic submucosal neurofibroma.A detailed history and physical examination did not reveal any evidence of extraintestinal neurofibromatosis.He underwent transanal surgical resection of the tumor.The patient tolerated the procedure well without any complications.CONCLUSION While neurofibromas have been well described in literature,an isolated colonic neurofibroma is a rare pathological entity.Malignant transformation of neurofibromas has been reported in patients with neurofibromatosis syndromes.We report a case of isolated colonic neurofibroma and highlight the importance of resection due to the increased risk of tumorigenesis.

Clinical and scientific innovations in auditory brainstem implants

The auditory brainstem implant(ABI)was originally developed to provide rehabilitation of retrocochlear deafness caused by neurofibromatosis type 2(NF2).Recent studies of the ABI have investigated outcomes in non-NF2 cohorts,such as patients with cochlear nerve aplasia or cochlear ossification and more recently,intractable tinnitus.New technologies that improve the ABI-neural tissue interface are being explored as means to improve performance and decrease side effects.Innovative discoveries in optogenetics and bioengineering present opportunities to continually evolve this technology into the future,enhancing spatial selectivity of neuronal activation in the cochlear nucleus and preventing side effects through reduction in activation of non-target neuronal circuitry.These advances will improve surgical planning and ultimately improve patients1 audiological capabilities.ABI research has rapidly increased in the 21st century and applications of this technology are likely to continually evolve.Herein,we aim to characterize ongoing clinical,basic science,and bioengineering advances in ABIs and discuss future directions of this technology.