Clinical Study Trigeminal schwannomas: Experience with 68 cases Bhawani Shankar Sharma * , Faiz Uddin Ahmad, Poodipedi Sarat Chandra, Ashok Kumar Mahapatra Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi 110 029, India Received 19 June 2006; accepted 8 September 2006 Abstract Trigeminal schwannomas (TS) are rare. Only a couple of series involving a large number of cases have been reported. In the present study we aimed to analyse the clinical characteristics of TS, the surgical approaches used to treat TS, and the outcomes for patients undergoing surgical treatment for TS via retrospective analysis of departmental records. Data for 68 patients treated for TS in the Department of Neurosurgery at the All India Institute of Medical Sciences between January 1993 and December 2005 were analysed. Most patients were in the fourth decade of life, with the duration of symptoms ranging from 1 month to 13 years. Twenty-nine TSs were classified as type A, 13 as type B and 26 as type C, depending upon size. A skull base approach was used in every surgically treated case. Of the 46 patients for whom radiological follow-up data were available, complete tumour excision was achieved in 35 cases (76%). Fol- low-up ranged from 3 months to 12 years (mean 62 months). One patient died and nine (15%) had permanent morbidity in the form of corneal opacity (5) or facial (2) or trochlear (2) nerve palsy. We conclude that trigeminal neuromas are best treated by total surgical resection, which yields acceptable results with low rates of mortality and permanent morbidity. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Trigeminal schwannoma; Management; Outcome 1. Introduction Schwannomas arising from the trigeminal nerve are rare, constituting only 0.1–0.4% of all intracranial tumours and 1–8% of all intracranial schwannomas. 1–10 Only a cou- ple of large case series of trigeminal schwannoma (TS) have been reported in the literature. 1–3 The surgical approach that is most appropriate for these tumours remains contro- versial. We report our experience of 68 of these tumours. 2. Subjects and methods Between January 1993 and December 2005, 68 patients were treated for TS in the Department of Neurosurgery at the All India Institute of Medical Sciences, New Delhi. Data were retrospectively collected from the hospital re- cords and analysed. 2.1. Patient population Of 68 patients, 46 were male and 22 were female (ratio of 2:1). The ages of the patients ranged from 16 to 62 years, with a mean of 38 years. The left side (41 patients [60%]) was involved more commonly than the right (27 patients [40%]). Most patients were young to middle-aged, with the largest number of patients in the fourth decade of life. The duration of symptoms ranged from 1 month to 13 years. Facial pain and paraesthesias were the most com- mon presenting symptoms, being present in 62 cases (91%). After the trigeminal nerve, the seventh cranial nerve was the next most commonly involved nerve (24 cases; 35%). Other cranial nerves were also commonly involved. Notably, the lower cranial nerves were involved in 17 cases. Raised intracranial pressure (ICP) was present in 35 pa- tients (51%). Five patients presented with altered senso- rium (Table 1). Either CT or MRI was carried out for 26 patients, and 42 patients underwent both CT and MRI. 0967-5868/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2006.09.007 * Corresponding author. Tel.: +91 11 26584573. E-mail address: [email protected](B.S. Sharma). www.elsevier.com/locate/jocn Available online at www.sciencedirect.com Journal of Clinical Neuroscience 15 (2008) 738–743
Transcript
Available online at www.sciencedirect.com
www.elsevier.com/locate/jocn
Journal of Clinical Neuroscience 15 (2008) 738–743
Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi 110 029, India
Received 19 June 2006; accepted 8 September 2006
Abstract
Trigeminal schwannomas (TS) are rare. Only a couple of series involving a large number of cases have been reported. In the presentstudy we aimed to analyse the clinical characteristics of TS, the surgical approaches used to treat TS, and the outcomes for patientsundergoing surgical treatment for TS via retrospective analysis of departmental records. Data for 68 patients treated for TS in theDepartment of Neurosurgery at the All India Institute of Medical Sciences between January 1993 and December 2005 were analysed.Most patients were in the fourth decade of life, with the duration of symptoms ranging from 1 month to 13 years. Twenty-nine TSs wereclassified as type A, 13 as type B and 26 as type C, depending upon size. A skull base approach was used in every surgically treated case.Of the 46 patients for whom radiological follow-up data were available, complete tumour excision was achieved in 35 cases (76%). Fol-low-up ranged from 3 months to 12 years (mean 62 months). One patient died and nine (15%) had permanent morbidity in the form ofcorneal opacity (5) or facial (2) or trochlear (2) nerve palsy. We conclude that trigeminal neuromas are best treated by total surgicalresection, which yields acceptable results with low rates of mortality and permanent morbidity.� 2007 Elsevier Ltd. All rights reserved.
Schwannomas arising from the trigeminal nerve arerare, constituting only 0.1–0.4% of all intracranial tumoursand 1–8% of all intracranial schwannomas.1–10 Only a cou-ple of large case series of trigeminal schwannoma (TS) havebeen reported in the literature.1–3 The surgical approachthat is most appropriate for these tumours remains contro-versial. We report our experience of 68 of these tumours.
2. Subjects and methods
Between January 1993 and December 2005, 68 patientswere treated for TS in the Department of Neurosurgeryat the All India Institute of Medical Sciences, New Delhi.Data were retrospectively collected from the hospital re-cords and analysed.
0967-5868/$ - see front matter � 2007 Elsevier Ltd. All rights reserved.
Of 68 patients, 46 were male and 22 were female (ratioof 2:1). The ages of the patients ranged from 16 to 62 years,with a mean of 38 years. The left side (41 patients [60%])was involved more commonly than the right (27 patients[40%]). Most patients were young to middle-aged, withthe largest number of patients in the fourth decade of life.The duration of symptoms ranged from 1 month to 13years. Facial pain and paraesthesias were the most com-mon presenting symptoms, being present in 62 cases(91%). After the trigeminal nerve, the seventh cranial nervewas the next most commonly involved nerve (24 cases;35%).
Other cranial nerves were also commonly involved.Notably, the lower cranial nerves were involved in 17 cases.Raised intracranial pressure (ICP) was present in 35 pa-tients (51%). Five patients presented with altered senso-rium (Table 1). Either CT or MRI was carried out for 26patients, and 42 patients underwent both CT and MRI.
B.S. Sharma et al. / Journal of Clinical Neuroscience 15 (2008) 738–743 739
Tumor extension was classified as described by Samiiet al.10: Type A, intracranial tumour predominantly inthe middle fossa (29 patients); type B, intracranial tumour
Fig. 1. T2-weighted (a,b) axial and (c) sagittal MR images showing a heterogen(b, c) The tumour is brightly enhancing on contrast administration. (d) Post-o
predominantly in the posterior fossa (13 patients); type C,intracranial dumbbell-shaped tumour in the middle andposterior fossa (26 patients); and type D, extracranial tu-mour with intracranial extension (no patients). Surgical ap-proaches were chosen depending on the primary locationof the tumour. Large tumours were operated on (e.g.Fig. 1) and small tumours (less than 3 cm in size) were usu-ally given gamma knife treatment (Fig. 2).
3. Results
Fifty-eight patients underwent definitive surgery, and 10patients (with tumours smaller than 3 cm in size) weregiven primary gamma knife treatment. Of 35 patientswho presented with raised ICP, 10 had failing vision requir-ing insertion of a ventriculoperitoneal shunt for hydro-cephalus before definitive surgery.
eously hyperintense tumour in both the middle and posterior cranial fossa.perative sagittal CT scan showing complete tumour removal.
Fig. 2. Contrast-enhanced axial T1-weighted MRI showing a smalldumbbell-shaped tumour arising in the right Meckel’s cave.
740 B.S. Sharma et al. / Journal of Clinical Neuroscience 15 (2008) 738–743
A skull-base approach was used for every surgicallytreated case. Middle fossa-subtemporal craniotomy wascarried out in 26 cases (extradural approach in eight, andcombined extradural/intradural approach in 18 cases).The middle fossa-subtemporal craniotomy was combinedwith an orbitozygomatic craniotomy in an additional 15cases. A retromastoid route was used for type B tumoursin 12 cases. Three patients underwent staged surgery (retro-mastoid followed by a subtemporal route). A combinedpresigmoid-subtemporal approach was employed in twocases. In 48 patients, complete tumour excision was per-formed (Table 2).
There was one death in our series. The patient who diedwas admitted in coma and underwent a ventriculoperitonealshunt as an emergency procedure for hydrocephalus, thendeveloped meningitis after definitive surgery and died aftera complicated post-operative course. Permanent morbiditywas seen in nine patients (15%) in the form of corneal ulcer-ation in five patients and facial palsy and fourth nerve def-icits in two patients each. Temporary morbidity was muchmore common: meningitis developed in five patients, chestinfection in four patients, cerebrospinal fluid otorrhoeaand facial paresis in three each and hemiparesis, and thirdand fourth nerve paresis in two each. Transient worseningof facial hypoaesthesia was common after surgery. All pa-
Table 2Treatment administered to patients with trigeminal schwannoma
Treatment No.
Surgery 58Ventriculoperitoneal shunt 10
Definitive surgeryMiddle fossa subtemporal approach (ED 8, combined ED+ID 18) 26Orbitozygomatic craniotomy and extended middle fossa approach 15Retromastoid 12Staged surgery (RM and ST) 3Presigmoid subtemporal 2
tients who underwent surgery had histologically verified be-nign schwannomas. There were no malignant tumours inour series.
The follow-up period ranged from 3 months to 12 years,with a mean of 62 months. A total of 46 patients had fol-low-up imaging, which revealed no residual tumour in 35cases and residual tumour in 11 cases. Five patients withlarge residual tumours on post-operative follow-up imag-ing were reoperated on later (two by a retrosigmoid routeand three by a subtemporal route).
Gamma knife (GK) therapy was carried out using aLeksell gamma knife (Elekta Instruments, Atlanta, GA,USA), with a tumour margin dose of 12–13 Gy, to pa-tients after May 1997 (time of installation) at the Gam-ma Knife Center in the Department of Neurosurgery.Primary GK treatment was given to 10 patients, andsix patients received GK in the post-operative periodfor small residual (5) and recurrent (1) tumours. Themean volume of tumour that underwent primary GKand adjuvant GK was 3.4 and 3.2 cm3, respectively. Ofthe 10 patients with at least 6 months of follow up (mean18.7 months, range 6–37 months), five improved clini-cally, but two worsened. Of the two patients who wors-ened, one patient (4.5 cm3 tumour volume) developedthird nerve paresis at 1 year follow-up, and the other,who had a 9.9 cm3 tumour, developed gait ataxia dueto perilesional oedema at 8 months. The mean radiolog-ical follow-up was 15.7 months (range 6–37 months) andthere was a tumour growth control rate of 85.75%. Themean volumes of tumours that decreased in size, re-mained stable and increased in size were 2.11, 5.33 and8.1 cm3, respectively.
4. Discussion
Cranial nerve involvement was a common presentingsymptom in our series, similar to the findings of other stud-ies.1,2,11,12 In 1999 Yoshida and Kawase6 reviewed the clin-ical features of 402 cases previously reported in theliterature. Trigeminal nerve dysfunction was observed inmore than 70% of cases. Abducens nerve paresis was seenin 26% of cases, closely followed by involvement of the sev-enth–eighth nerve complex. Less than 10% of patients hadlower cranial nerve involvement. Samii et al.20 found nolower cranial nerve palsy, whereas it was observed in 25%of our cases. This is probably because of the large size ofthe tumours seen in the Indian subcontinent, a fact sup-ported by an early observation.1,2
Tumours arising from the ganglion usually cause con-stant pain, in contrast to tumours arising in the root, forwhich pain is frequently absent. However, we found thatfacial pain is not a common feature of TS, and facial hypo-aesthesia is much more common than facial pain.11–13
Some authors have found pathological laughter as an earlypresenting symptom in massive trigeminal neuromas.1,2
Thirty-five (51%) of our patients presented with raisedICP, either because of the large size of the tumour or
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associated hydrocephalus. Due to failing vision and detec-tion of hydrocephalus on CT, 10 patients required insertionof a ventroperitoneal shunt as an emergency procedure be-fore definitive surgery. Five patients presented with alteredsensorium, owing to late presentation and the large sizes oftheir tumours.
High-resolution CT clearly demonstrates the locationand extent of tumour growth and bone changes.15–17 Gen-erally, TS are iso-hyperdense uniformly enhancing lesions.MRI offers additional advantages, including the ability toobtain sagittal views, the lack of streak artefacts due tobone, demonstration of extracranial extension, visualisa-tion of vascular structures in relation to the lesion, dis-placement of normal brain structures, relationship to thecavernous sinus/tentorium, and atrophy of masseter andpterygoid muscles on coronal scans.18,19 TS are iso- orslightly hypointense on T1 weighted images, with signifi-cant enhancement after gadolinium injection. We preferto obtain both CT scans and MR images for all patientswith TS, as they reveal complementary findings.
Multiple attempts at TS classification have been at-tempted in the interests of supporting the choice of surgicalstrategy.6,10,20,21 Jefferson20 classified TS into three types(types A, B, C) depending upon their location in the middlefossa, posterior fossa or both. Samii at al.10 added type Dto this classification to represent tumours arising predomi-nantly in the extracranial space. TS were classified into sixtypes by Yoshida and Kawase6 according to tumour loca-tion. We used the classification of Samii et al.10 in the pres-ent study.
The location and size of the TS dictates the most appro-priate approach.1–7,21–28 Tumours are usually easily separa-ble from the cavernous sinus and the carotid artery, whichfacilitates their radical removal. Often, the tumour doesnot completely destroy the trigeminal nerve, and can beseparated from its fascicles while preserving neurologicalfunction.
Complete removal of the tumour should be the aim, butnot at the cost of neurological function. However, transientneurological dysfunction is common after surgery. Skullbase approaches minimize brain retraction, shorten the dis-section distance and provide multiple entry points for tu-mour resection.21 This provides a direct and a wideangled surgical field, and effectively makes a deep lesionsuperficial. For trigeminal schwannomas of the middlefossa, the preferred route is subtemporal.5 Many of thesetumours can also be removed through a purely extraduralapproach using large and extensive basal osteotomiescombined with petrosectomy. In large tumours, the thirdto tenth cranial nerves may be adherent to the capsule.The cavitron ultrasonic surgical aspirator is useful for int-ratumoural decompression. Blood vessels and nervesshould be dissected free first before removal of the capsule.
We used an extradural approach in eight cases,achieving total excision without any post-operative mor-bidity in these cases. We feel that this is the best ap-proach for peripheral-type or ganglion-type tumours.
This avoids or reduces significantly the complicationsassociated with brain retraction, vascular and neuralinjuries and cerebrospinal fluid leak, thus reducingpost-operative morbidity. For dumbbell tumours extend-ing into both the middle and posterior fossa, a combinedsubtemporal intradural transtentorial approach may benecessary for total extirpation. Staged surgery (removalof the tumour in two sittings using two different ap-proaches) was carried out in two of our cases. Forpure/predominant posterior fossa tumours, a retromas-toid approach is most convenient and is familiar to mostneurosurgeons.
Goel and colleagues1,2,14,29 used several approaches fortreating TS, but found three approaches to be most appro-priate for treatment of these tumours: the infratemporalfossa interdural approach, the lateral basal subtemporalapproach, and the retrosigmoid approach.
Schisano and Olivecrona8 reviewed the world literatureprior to 1956, and reported a 1-year mortality rate of41%. However, in recent years outcomes have improveddramatically with the use of microneurosurgery andskull-base approaches.7,9,22
The largest series (111 patients) in the literature relatingto TS was presented by Konovalov et al.3 Of 98 cases withlong-term follow up (average 13.5 years), 87% had good toexcellent results, with 12% symptomatic recurrence and 3%mortality. The second-largest series, involving 73 cases ofTS, was presented by Goel et al.1 This series also had thelargest average tumour size. Total tumour excision wasachieved in 51 cases (70%). Two patients died during thepost-operative period. With an average follow-up periodof 38 months, there was recurrence in one case and 71 pa-tients were leading independent lives. Yasui et al.9 usedskull-base approaches in treating eight cases of TS over13 years. There was no operative mortality; all patientshad a good/excellent outcome, and two cases hadrecurrences.
In the last 15–20 years, total or near-total removal hasbeen achieved in at least 70% of cases. The major impedi-ments to complete removal are inadequate exposure andinvolvement of the cavernous sinus.7–9 GK surgery is a via-ble option for small TSs, and achieves a tumour growthcontrol rate of more than 90%.30
The natural history of these tumours following subtotalexcision is not known; some authors have found a highincidence of symptomatic tumour growth following subto-tal excision,7 whereas others have found long periods ofremission.23 In elderly or medically unfit patients and withtumours with firm adherence to the brainstem, cranialnerves or blood vessels, subtotal tumour excision may stillbe the optimal treatment. However, it should result in sig-nificant relief of the patient’s symptoms. We prefer toadminister GK therapy to patients with small residual tu-mours. Those with large recurrences are best treated withrepeat surgery.
Different skull-base approaches have their own advan-tages and disadvantages. The extradural subtemporal
742 B.S. Sharma et al. / Journal of Clinical Neuroscience 15 (2008) 738–743
approach is very useful for both type A (predominantmiddle fossa) and type C (dumbbell tumours) TSs. It al-lows safe removal of cavernous sinus and infratemporalextensions. Al-Mefty et al.4 observed that even posteriorfossa extensions can be removed through the enlargedMeckel’s cave, without sectioning the tentorium or drillingthe petrous apex. Only large caudal extensions cannot bereached in this way. However, the extradural approachhas some disadvantages too. First, craniectomy andreconstruction of the dura mater in the cranial base canincrease the risk of opening air cells and cerebrospinalfluid leakage. Second, limited exposure of the intracranialspace can lead to repeated retraction of the brain tissue,thus leading to temporal lobe contusion. However, addi-tion of zygomatic osteotomy improves exposure and de-creases the risk of retraction contusions. Thesuboccipital retrosigmoid approach is a good approachfor tumours in the posterior cranial fossa and those withsmall middle fossa extensions. After exposure, the tumouris cored piecemeal between the tentorium cerebelli and thetrigeminal nerve. After being significantly debulked in thisway, the tumour can be resected using conventional tech-niques along with the right interface first in the infratento-rial region, then in the supratentorial region. Thisapproach has several advantages, such as easy exposure,and less traumatic injury to the brain under direct visual-isation, thus protecting important nerves and blood ves-sels in the cerebellopontine angle. For dumbbell tumourswith two parts of near equal size in both the middleand posterior cranial fossa, the temporal base transtento-rial approach is also suitable. Compared with other epidu-ral approaches, the temporal base transtentorial approachhas some advantages. First, temporal craniotomy is easilyperformed, with less bone removed in the middle cranialbase and minimal risk of opening mastoid air cells andsubsequent cerebrospinal fluid leakage. Second, when theposterior temporal lobe is retracted, the tumour in themiddle cranial fossa (i.e. intracavernous region) can be ex-posed more adequately, and the cavernous sinus and thecranial nerves and blood vessels in its medial aspect canbe directly visualised. Third, the posterior cranial fossaand the cerebellopontine angle can be reached after inci-sion of the tentorium cerebelli. The tumour in these re-gions is then safely removed under direct visualisation.Also, special reconstruction is unnecessary because of lim-ited bone removal of the middle cranial base.
5. Conclusion
TSs are rare tumours that are best treated by total sur-gical resection, which yields acceptable results with lowrates of mortality and permanent morbidity. Subtotalresection is appropriate for tumours with adhesions to vitalstructures and in medically unfit patients. Small recur-rences should be treated with GK therapy, whereas largerones are best dealt with using repeat surgery.
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