Spinal cord subependymoma

Spinal cord subependymoma

spinal cord subependymoma (SCSE) is a benign, non-invasive, slow-growing, WHO Grade I spinal cord tumor 1), first reported by Boykin et al. in 19542).

Epidemiology

Their most common site of occurrence is the fourth ventriclefollowed by the lateral ventricles. Spinal cord subependymomas typically manifest as cervical and cervicothoracic intramedullary or, rarely, extramedullary mass lesions.

Pathology

Histologically, there are hypocellular areas with occasional clusters of cells and frequent microcystic changes, calcifications, and hemorrhage. Radiologically, subependymomas generally manifest as eccentric well circumscribed nodular lesions with mild-to-moderate enhancement.

Clinical features

They often present clinically with pain and neurologic symptoms, including motor, sensory, urinary, and sexual dysfunction.

Diagnosis

Toi et al., made an important discovery of what seems to be a characteristic appearance for spinal subependymoma on sagittal MRI. Swelling of the spinal cord is extremely steep, providing unusually large fusiform dilatation resembling a bamboo leaf. They termed this characteristic MRI appearance as the “bamboo leaf sign.” This characteristic was apparent in 76.2% of cases of spinal subependymoma for which MRI findings were reported. Conclusion. The bamboo leaf sign on spinal MRI is useful for differentiating between subependymoma and other intramedullary tumors. Neurosurgeons encountering the bamboo leaf sign on spinal MRI should consider the possibility of subependymoma 3).

Differential diagnosis

It is not easily differentiable from a spinal cord ependymoma with radiological findings.

Treatment

Spinal cord subependymomas are not dissected easily from the spinal cord. Considering the rather indolent nature of spinal cord subependymomas, subtotal removal without the risk of neurological deficit is another option 4).

Outcome

Surgical findings and outcomes differ from those of an ependymoma, including a high risk of neurological deficit in the event of a poor dissection plane from the spinal cord with a low rate of recurrence.

Case series

Mikula et al., present a series of spinal cord subependymomas with a detailed description of the clinical, radiological and pathological features, and characterization by chromosomal microarray analysis. Briefly, the four patients included two men and two women, between the ages of 22 and 48 years. The most common presenting symptoms were neck and arm pain with upper extremity weakness. By imaging, the tumors were found to involve multiple spinal levels, including cervical/ cervico-thoracic (three patients) and thoracic (one patient), were all eccentric, and had minimal to no post-contrast enhancement. Two patients underwent gross total resection, one had a sub-total resection, and one underwent biopsy alone with a decompressive laminectomy. Follow up ranged from 6 months to 22 years. One patient (case 4) had recurrence 15 years following gross total resection and chromosomal microarray analysis revealed deletions on the long arm of chromosome 6. Our limited series suggests that spinal cord subependymomas can rarely recur, even following gross total resection, suggesting a possible role for long-term surveillance for these rare tumors5).


Yuh et al., retrospectively reviewed the medical records of ten spinal cord subependymoma patients (M : F=4 : 6; median 38 years; range, 21-77) from four institutions.

The most common symptoms were sensory changes and/or pain in eight patients, followed by motor weakness in six. The median duration of symptoms was 9.5 months. Preoperative radiological diagnosis was ependymoma in seven and astrocytoma in three. The tumors were located eccentrically in six and were not enhanced in six. Gross total resection of the tumor was achieved in five patients, whereas subtotal or partial resection was inevitable in the other five patients due to a poor dissection plane. Adjuvant radiotherapy was performed in two patients. Neurological deterioration occurred in two patients; transient weakness in one after subtotal resection and permanent weakness after gross total resection in the other. Recurrence or regrowth of the tumor was not observed during the median 31.5 months follow-up period (range, 8-89).

Spinal cord subependymoma should be considered when the tumor is located eccentrically and is not dissected easily from the spinal cord. Considering the rather indolent nature of spinal cord subependymomas, subtotal removal without the risk of neurological deficit is another option 6).

Case reports

A 51-year-old man presented with a 2-year history of progressive muscle weakness in the right lower extremity. Sagittal magnetic resonance imaging (MRI) showed spinal cord expansion at the Th7-12 vertebral level. Surgical resection was performed and the tumor was found to involve predominantly subpial growth. Histological diagnosis was subependymoma, classified as Grade I according to criteria of World Health Organization. They made an important discovery of what seems to be a characteristic appearance for spinal subependymoma on sagittal MRI. Swelling of the spinal cord is extremely steep, providing unusually large fusiform dilatation resembling a bamboo leaf. They termed this characteristic MRI appearance as the “bamboo leaf sign.” This characteristic was apparent in 76.2% of cases of spinal subependymoma for which MRI findings were reported. Conclusion. The bamboo leaf sign on spinal MRI is useful for differentiating between subependymoma and other intramedullary tumors. Neurosurgeons encountering the bamboo leaf sign on spinal MRI should consider the possibility of subependymoma 7).


A case report of a single patient in whom a subependymoma was resected from the cervical spinal cord with return to normal functioning.

Clinical examination, magnetic resonance imaging evaluation, surgical resection, and histological analysis were performed for diagnosis and treatment of this patient.

The patient experiencing myelopathy symptoms underwent a surgical resection of cervical spinal cord subependymoma that resulted in return to normal function.

Subependymoma should be included in the differential diagnosis of atypical presentations for myelopathy, as discrete surgical resection can result in good outcome 8).


A 53 year old man with a progressive paraparesis, paraesthesias of the lower limbs and sphincter disturbance. The tumour was partly removed, without progression 5 years after surgery 9).

References

1)

Im SH, Paek SH, Choi YL, Chi JG, Kim DG, Jung HW, Cho BK. Clinicopathological study of seven cases of symptomatic supratentorial subependymoma. J Neurooncol. 2003 Jan;61(1):57-67. PubMed PMID: 12587796.
2)

BOYKIN FC, COWEN D, IANNUCCI CA, WOLF A. Subependymal glomerate astrocytomas. J Neuropathol Exp Neurol. 1954 Jan;13(1):30-49. PubMed PMID: 13118373.
3) , 7)

Toi H, Ogawa Y, Kinoshita K, Hirai S, Takai H, Hara K, Matsushita N, Matsubara S, Uno M. Bamboo Leaf Sign as a Sensitive Magnetic Resonance Imaging Finding in Spinal Subependymoma: Case Report and Literature Review. Case Rep Neurol Med. 2016;2016:9108641. doi: 10.1155/2016/9108641. Epub 2016 Dec 15. PubMed PMID: 28074165; PubMed Central PMCID: PMC5198089.
4) , 6)

Yuh WT, Chung CK, Park SH, Kim KJ, Lee SH, Kim KT. Spinal Cord Subependymoma Surgery : A Multi-Institutional Experience. J Korean Neurosurg Soc. 2018 Mar;61(2):233-242. doi: 10.3340/jkns.2017.0405.001. Epub 2018 Feb 28. PubMed PMID: 29526067; PubMed Central PMCID: PMC5853201.
5)

Mikula AL, Paolini MA, Sukov WR, Clarke MJ, Raghunathan A. Subependymoma involving multiple spinal cord levels: A clinicopathological case series with chromosomal microarray analysis. Neuropathology. 2019 Mar 11. doi: 10.1111/neup.12543. [Epub ahead of print] PubMed PMID: 30856298.
8)

Cure LM, Hancock CR, Barrocas AM, Sternau LL, C Hirzel A. Interesting case of subependymoma of the spinal cord. Spine J. 2014 May 1;14(5):e9-12. doi: 10.1016/j.spinee.2013.10.056. Epub 2013 Nov 20. PubMed PMID: 24269267.
9)

Dario A, Fachinetti P, Cerati M, Dorizzi A. Subependymoma of the spinal cord: case report and review of the literature. J Clin Neurosci. 2001 Jan;8(1):48-50. PubMed PMID: 11148079.

Hearing loss after microvascular decompression for hemifacial spasm

Hearing loss after microvascular decompression for hemifacial spasm

Risk factors

The cochlear nerve function is at risk during microvascular decompression for hemifacial spasm.

Cause and risk factors are highly variable.

A study strongly suggested a correlation between the cerebellar retraction factors, especially retraction depth and duration, and possibility of hearing loss following MVD for HFS 1).

Intradural compression due to overinfusion of saline may lead to postoperative hearing loss, although the incidence is low, and immediate decompression by drainage may be required 2).

Prevention

Intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) can be a useful tool to decrease the danger of hearing loss 3) 4) 5).

It is important to emphasize the need for clean exposure of the lower cranial nerves (except for cranial nerve VIII) to obtain enough working space, sharp arachnoid dissection, minimal cerebellar retraction, and proper responses to changes identified during intraoperative monitoring 6).

Diagnosis

Prolongation of the inter-peak latency of waves I-III seems to be associated with the occurrence of delayed hearing loss. It is possible that BAEP changes may predict delayed hearing loss, but confirmatory evidence is not available as yet. Analysis of more cases is necessary to determine the utility of BAEP monitoring to predict delayed hearing loss after MVD and to identify its exact cause 7).

Case series

Lee et al., from the Samsung Medical Center in a study aimed to analyze cases of delayed hearing loss after microvascular decompression (MVD) for hemifacial spasm and identify the characteristic features of these patients.

They retrospectively reviewed the medical records of 3462 patients who underwent MVD for hemifacial spasm between January 1998 and August 2017.

Among these, there were 5 cases in which hearing was normal immediately postoperatively but delayed hearing loss occurred. None of the 5 patients reported any hearing disturbance immediately after the operation. However, they developed hearing problems suddenly after some time (median, 22 days; range 10-45 days). On examination, sensorineural hearing loss was confirmed. High-dose corticosteroid treatment was prescribed. Preoperative hearing levels were restored after several months (median duration from the time of the operation, 45 days; range 22-118 days). Interestingly, the inter-peak latency of waves I-III in the brainstem auditory evoked potentials (BAEP) was prolonged during the surgery, but recovered within a short time.

Delayed hearing loss may occur after MVD for HFS. Prolongation of the inter-peak latency of waves I-III seems to be associated with the occurrence of delayed hearing loss. It is possible that BAEP changes may predict delayed hearing loss, but confirmatory evidence is not available as yet. Analysis of more cases is necessary to determine the utility of BAEP monitoring to predict delayed hearing loss after MVD and to identify its exact cause 8).


Nine hundred and thirty-two patients with HFS who underwent MVD with intraoperative monitoring (IOM) of BAEP were analyzed. Park et al., used a 43.9 Hz/s stimulation rate and 400 averaging trials to obtain BAEP. To evaluate HL, pure-tone audiometry and speech discrimination scoring were performed before and one week after surgery. We analyzed the incidence for postoperative HL according to BAEP changes and calculated the diagnostic accuracy of significant warning criteria.

Only 11 (1.2%) patients experienced postoperative HL. The group showing permanent loss of wave V showed the largest percentage of postoperative HL (p < 0.001). No patient who experienced only latency prolongation (≥1 ms) had postoperative HL. Loss of wave V and latency prolongation (≥1 ms) with amplitude decrement (≥50%) were highly associated with postoperative HL.

Loss of wave V and latency prolongation of 1 ms with amplitude decrement ≥50% were the critical warning signs of BAEP for predicting postoperative HL 9).


Jung et al., retrospectively analyzed the medical records of patients with HFS who underwent MVD with the same surgeon from March 2003 to October 2016, and reviewed the pertinent literature. Patients who were followed up for more than 6 months were selected, resulting in the analysis of 1434 total patients. Postoperative hearing complications were evaluated audiometrically and subjectively (patient-reported symptoms). Clinical factors such as the intraoperative findings were reviewed to identify their correlation with auditory function.

Symptoms in 1333/1434 patients (93.0%) resolved more than 90% from their preoperative state. Among them, 16 patients (1.1%) complained of hearing impairment after surgery. Most impairment was transient, although 6/1333 patients (0.4%) required additional interventions for persistent hearing deficits (one surgical intervention and five hearing aids). A >50% decrease in the amplitude of brainstem auditory evoked potentials during the operation was significantly associated with postoperative hearing deficits.

Few auditory complications, mostly transient, result from MVD. Although MVD is a commonplace surgical technique, to reduce complications it is important to emphasize the need for clean exposure of the lower cranial nerves (except for cranial nerve VIII) to obtain enough working space, sharp arachnoid dissection, minimal cerebellar retraction, and proper responses to changes identified during intraoperative monitoring 10)


Three hundred thirty-one patients with HFS underwent MVD from March 2009 to October 2010.

Brain stem auditory evoked potential (BAEP) was monitored during the surgery. Before completion of the dural closure, the surgical field was routinely filled with warm saline to avoid postoperative pneumocephalus and epidural hematoma.

Seven patients experienced a change in wave V amplitude and latency after the dural closure. In 2 patients, the amplitudes decreased by less than 50%, and latencies were delayed by less than 1.0 ms, ipsilaterally in 1 patient and contralaterally in the other. In 1 patient, decreased amplitude and delayed latency appeared bilaterally with more severity on the operated side, accompanied by delayed ipsilateral permanent hearing loss. In 4 of the 7 patients, an ipsilateral response of BAEP was completely absent. Of these 4 patients, 2 experienced permanent hearing loss, and another 2 patients who underwent dural reopening and saline drainage had restoration of their normal hearing.

Intradural compression due to overinfusion of saline may lead to postoperative hearing loss, although the incidence is low, and immediate decompression by drainage may be required 11).


668 patients (95.7%) had no hearing loss immediately after surgery (group 1). 17 patients (2.4%) had a postoperative decrease in PTA exceeding 15 dB and a decrease in SDS which was proportional to the postoperative PTA thresholds (group 2). Eight patients (1.2%) had poor SDS that appeared to be out of proportion to the degree of hearing loss depicted by the postoperative PTA thresholds, suggesting retrocochlear or cochlear nerve pathology (group 3). Five patients (0.7%) had total deafness after surgery (group 4). In group 2, 12 patients (70.6%) returned to their preoperative hearing capacity. However, among the eight patients in group 3 and five in group 4, only two (25%) and none (0%) have returned to their preoperative hearing status, respectively.

In this large study, permanent hearing loss occurred in 16 patients (2.2%). Patients with a mild hearing loss with a good SDS (cochlear type) demonstrated much better prognosis than those with poor SDS (retrocochlear type) or total deafness. In addition, total deafness after surgery had no chance of recovery to preoperative hearing capacity 12).


Auditory function was studied before and after surgery in 143 consecutive patients who were operated on for hemifacial spasm by microvascular decompression of the intracranial portion of the facial nerve. The acoustic reflex was abnormal preoperatively in 41% of the patients, indicating that the vascular abnormalities that caused the hemifacial spasm also affected the auditory nerve. Three patients suffered a profound hearing loss in the ear on the operated side, and one lost hearing function totally. In addition, 24 patients had a moderate elevation in the pure-tone threshold at one or more octave frequencies. Of these, 16 patients experienced a hearing loss at only one frequency (8000 Hz), while eight had a threshold evaluation of no more than 20 dB in the speech frequency range (500, 1000, and 2000 Hz). Two patients were deaf on the side of the spasm before the operation. Three patients were not tested postoperatively, and one patient was tested only after surgery. Thus, in this series of 143 patients, only 2.8% suffered a significant hearing loss as a complication of facial nerve decompression to relieve hemifacial spasm 13).

Case reports

Onoda et al., reported two unusual cases of delayed hearing loss after microvascular decompression (MVD) for hemifacial spasm. In the first case, A 59-year-old female noted left hearing loss one week after receiving MVD for left hemifacial spasm. In the second case, A 39-year-old male also noticed ipsilateral hearing loss on the 7th day after MVD for right hemifacial spasm. Both cases were treated by steroid. Two months after the onset, their hearing function improved dramatically. These cases indicated that the delayed hearing loss after MVD for hemifacial spasm can occur, even when gentle microsurgical technique is used, but the prognosis for this condition is fairly good 14).

References

1)

Li N, Zhao WG, Pu CH, Yang WL. Quantitative study of the correlation between cerebellar retraction factors and hearing loss following microvascular decompression for hemifacial spasm. Acta Neurochir (Wien). 2018 Jan;160(1):145-150. doi: 10.1007/s00701-017-3368-9. Epub 2017 Oct 26. PubMed PMID: 29075904.
2) , 11)

Jo KW, Lee JA, Park K, Cho YS. A new possible mechanism of hearing loss after microvascular decompression for hemifacial spasm. Otol Neurotol. 2013 Sep;34(7):1247-52. doi: 10.1097/MAO.0b013e31829b5786. PubMed PMID: 23942352.
3) , 7) , 8)

Lee MH, Lee S, Park SK, Lee JA, Park K. Delayed hearing loss after microvascular decompression for hemifacial spasm. Acta Neurochir (Wien). 2019 Mar;161(3):503-508. doi: 10.1007/s00701-018-3774-7. Epub 2018 Dec 19. PubMed PMID: 30569226.
4) , 9)

Park SK, Joo BE, Lee S, Lee JA, Hwang JH, Kong DS, Seo DW, Park K, Lee HT. The critical warning sign of real-time brainstem auditory evoked potentials during microvascular decompression for hemifacial spasm. Clin Neurophysiol. 2018 May;129(5):1097-1102. doi: 10.1016/j.clinph.2017.12.032. Epub 2018 Jan 4. PubMed PMID: 29342440.
5)

El Damaty A, Rosenstengel C, Matthes M, Baldauf J, Dziemba O, Hosemann W, Schroeder HWS. A New Score to Predict the Risk of Hearing Impairment After Microvascular Decompression for Hemifacial Spasm. Neurosurgery. 2017 Nov 1;81(5):834-843. doi: 10.1093/neuros/nyx111. PubMed PMID: 28973677.
6) , 10)

Jung NY, Lee SW, Park CK, Chang WS, Jung HH, Chang JW. Hearing Outcome Following Microvascular Decompression for Hemifacial Spasm: Series of 1434 Cases. World Neurosurg. 2017 Dec;108:566-571. doi: 10.1016/j.wneu.2017.09.053. Epub 2017 Sep 18. PubMed PMID: 28927910.
12)

Park K, Hong SH, Hong SD, Cho YS, Chung WH, Ryu NG. Patterns of hearing loss after microvascular decompression for hemifacial spasm. J Neurol Neurosurg Psychiatry. 2009 Oct;80(10):1165-7. doi: 10.1136/jnnp.2007.136713. PubMed PMID: 19762909.
13)

Møller MB, Møller AR. Loss of auditory function in microvascular decompression for hemifacial spasm. Results in 143 consecutive cases. J Neurosurg. 1985 Jul;63(1):17-20. PubMed PMID: 4009269.
14)

Onoda K, Ono S, Miyoshi Y, Tokunaga K, Date I. [Delayed hearing loss after microvascular decompression for hemifacial spasm: report of two cases]. No Shinkei Geka. 2006 Oct;34(10):1045-9. Review. Japanese. PubMed PMID: 17052017.
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