Cranial nerve schwannoma - A pictorial essay

Intraoperative visualization of cranial nerve schwannomas using second-window indocyanine green: A case series

BACKGROUND

Second Window Indocyanine Green (SWIG) is a novel intraoperative imaging technique that uses near-infrared (NIR) light for intra-operative tumor visualization using the well-known fluorophore indocyanine green (ICG). Because schwannomas often incorporate the nerve into the encapsulated tumor and impinge on surrounding neural structures, SWIG is a promising technique to improve tumor resection while sparing the nerve.

OBJECTIVE

To demonstrate the use of SWIG in resection of cranial nerve schwannomas.

METHODS

Three patients with cranial nerve schwannomas (i.e., trigeminal, vestibular, and vagus) underwent SWIG-guided resection. During surgery, NIR visualization was used intermittently used to detect fluorescence to guide resection. Signal-to-background ratio was then calculated to quantify fluorescence.

RESULTS

Patients were infused with ICG at a dose of 5.0 mg/kg 24 hours before surgery. Each patient achieved total or near-total resection and relief of symptoms with lack of recurrence at six-month follow-up. The average SBR calculated was 3.79, comparable to values for SWIG-guided resection of other brain and spine tumors.

CONCLUSION

This case series is the first published report of trigeminal and vagus nerve schwannoma resection using the SWIG technique and suggests that SWIG may be used to detect all schwannomas, alongside many other types of brain tumor. This paper also demonstrates the importance of preoperative ICG infusion timing and discusses the inverse pattern of NIR signal that may be observed when infusion occurs outside of the optimal timing. This provides direction for future studies investigating the administration of SWIG to resect cranial nerve schwannomas and other brain tumors.

Imaging of trochlear nerve schwannomas: a case series and systematic review of the literature

Purpose Trochlear nerve schwannomas are rare tumors. So far, only 121 cases have been published. We present four new cases, discuss the imaging characteristics and summarize all previously published cases through a systematic review.Methods Four cases, all treated in AZ Sint-Jan Hospital Brugge-Oostende (Belgium), were collected, including their demographic, clinical and radiological data. All MR imaging was performed with the three-dimensional fluid-attenuated inversion recovery (3D-FLAIR), turbo spin echo T1 high-resolution (TSE T1 HR), three-dimensional balanced fast-field echo (3D b-FFE) and three-dimensional T1 black blood (3D T1 black blood) sequence. We compared our findings with the present literature through a systematic literature review in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.Results Screening with routine unenhanced 3D-FLAIR imaging could identify all schwannomas as hyperintense lesions on the course of the trochlear nerve. The use of 3D T1 black blood sequences was superior in depicting the lesions, while high-resolution 3D b-FFE images enabled us to visualize the anatomic boundaries of the lesions in detail. Most trochlear schwannomas are located in the ambient cistern, at or just below the free edge of the tentorium.Conclusion The majority of trochlear nerve schwannomas are located cisternal and display variable enhancement on contrast administration. 3D-FLAIR imaging is superior in detecting these lesions. Comparison with data collected from previous cases demonstrates the importance of early diagnosis and treatment. Generally, patients with trochlear nerve schwannomas have a good prognosis.

Accessory nerve schwannoma extending into the fourth ventricle: case report and review of literature

Accessory nerve schwannoma is a rare entity in patients presenting with cranial nerve (CN) deficits. Most of these tumours arise from the cisternal segment of the eleventh CN and extend caudally. Herein, we report the third case of an accessory schwannoma extending cranially into the fourth ventricle. A 61-year-old female presented with a history of variable headaches. Cerebral magnetic resonance imaging (cMRI) revealed a large inhomogeneous contrast-enhancing lesion at the craniocervical junction extending through the foramen of Magendi and concomitant hydrocephalus due to obstruction of the foramina of Luschkae. Microsurgical tumour resection was performed in the half-sitting position. Intraoperatively, the tumour arose from a vestigial fascicle of the spinal accessory nerve. At three month follow-up, neither radiological tumour recurrence nor neurological deficits were observed.

A Rare Case of Cervical Vagal Nerve Schwannoma in a 30-Year-Old Ethiopian Man

Schwannoma is a slowly growing benign tumor that arises from Schwann cells. Schwannomas affect both genders equally. It occurs in any age group, but most cases are seen between the third and fifth decade. About one-fourth to one-third of extracranial schwannomas cases originate in the head and neck region. The vagus nerve, followed by the cervical sympathetic chain, is the leading site of origin in the neck region. The majority of patients with schwannomas are asymptomatic. Patients with vagal nerve schwannomas in the neck primarily present with hoarseness of voice due to paralysis of the vocal cords. Because of their rarity and the lack of a neurologic deficit as a presenting symptom, preoperative consideration of schwannomas is tough, and several differential diagnoses may be entertained.The mainstay of treatment for vagal nerve schwannoma is complete surgical excision. Here we present a rare case of cervical vagal nerve schwannoma in a 30-year-old male farmer from Ethiopia. The patient presented with a gradually increasing neck swelling of 10 years duration. He started to have hoarseness in his voice five months prior to his presentation. On examination, he had a huge anterior neck swelling. He had two FNAC results, which were inconclusive, and a neck CT. With the consideration of multinodular goiter versus spindle cell neoplasm, the neck was explored, and complete excision of the mass was done. The excisional biopsy turned out to be a classical cervical schwannoma. So this report aims to make physicians aware of the rare case of schwannomas, particularly vagal nerve schwannomas. Clinicians should consider schwannomas in the differential diagnosis of a patient presenting with a cervical mass. Furthermore, they need to be well aware of the diagnostic workup, mainly the imaging modalities, which are essential for proper preoperative planning, surgical treatment, and postoperative complications of cervical schwannomas.

The Treatment Outcome of CyberKnife-Based Stereotactic Radiotherapy for Intracranial and Extracranial Nonvestibular Schwannomas: A Single-Center Experience

BACKGROUND

Data on the outcomes of CyberKnife-based hypofractionated stereotactic radiosurgery (hSRS) for intracranial and extracranial nonvestibular schwannomas (nVSs) are not sufficient.

METHODS

Patients who underwent hSRS for nVSs between 2010 and 2019 were retrospectively reviewed.

RESULTS

A total of 39 patients with 39 nVSs were identified. The mean age was 53 (±18) years, and 20 patients (51%) were women. Twenty-five patients (64%) had previous surgeries. Seventeen patients (44%) had nVSs extending outside the cranium. The mean prescribed dose covering 95% of the planning target volume was 22 Gy (±3.7 Gy), the mean fractionation was 4 (±2), and the mean target volume was 13 cm³ (±16 cm³). The radiological tumor control rate was 100% during the mean follow-up period of 67 months (±37 months). Thirty-seven patients (95%) were clinically stable during the mean follow-up period of 72 months (±35 months). Nine patients (23%) suffered from transient adverse radiation effects (AREs), including transient tumor expansion, and 2 (5%) suffered from permanent AREs.

CONCLUSIONS

We summarized the treatment outcomes of hSRS for nVSs. Although all patients achieved radiological tumor control, the risk of either transient or permanent ARE was high. Therefore, it is necessary to monitor patients for clinical deterioration due to AREs.