CASE REPORTS TROCHLEAR NERVE SCHWANNOMA WITH INTRATUMORAL HEMORRHAGE: CASE REPORT Shigeo Ohba, M.D. Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan Tomoru Miwa, M.D. Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan Takeshi Kawase, M.D., Ph.D. Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan Reprint requests: Shigeo Ohba, M.D., Department of Neurosurgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan. Email: di045009@sc.itc.keio.ac.jp Received, June 30, 2005. OBJECTIVE AND IMPORTANCE: Schwannomas originating from the trochlear nerve without neurofibromatosis are extremely rare. Thirty-four cases have previously been reported in the literature, and only 25 cases were pathologically diagnosed. In addition, intratumoral hemorrhage in intracranial schwannomas is also rare. Approximately 30 cases of intracranial schwannomas with intratumoral hemorrhage have been reported. CLINICAL PRESENTATION: A 42-year-old man presented with left hemiparesis and right trochlear nerve palsy. Magnetic resonance imaging revealed an abnormal cystic lesion beside the brainstem. His symptoms rapidly worsened after enlargement of the mass because of intratumoral hemorrhage. INTERVENTION: Gross total removal of the tumor was performed via the anterior transpetrosal approach. The tip of the trochlear nerve was fanned out and unified with the tumor. The tumor was diagnosed as a schwannoma. CONCLUSION: The patient’s hemiparesis improved postoperatively, and he was discharged 1 week after the operation. Magnetic resonance imaging performed 4 months later revealed no regrowth of the tumor. Only right trochlear nerve palsy has persisted. This report is the second case of intratumoral hemorrhage from a trochlear nerve schwannoma. KEY WORDS: Intratumoral hemorrhage, Neurinoma, Schwannoma, Trochlear nerve Accepted, November 19, 2005. Neurosurgery 58:791, 2006 C ranial nerve schwannomas account for 8% of all intracranial tumors. Most of them arise from sensory nerves, commonly the vestibular nerve and less commonly the trigeminal nerve (12, 25). Schwannomas originating from motor nerves such as the oculomotor (12, 19), trochlear (12), and abducens nerves (12) are rare. There is an association of schwannomas with neurofibromatosis (6). Motor origin schwannomas not associated with neurofibromatosis are exceedingly rare. To our knowledge, 34 cases of trochlear nerve schwannomas have been reported in the literature (1, 2, 4–13, 17, 19–23, 26–33), and only 25 cases of them were pathologically diagnosed as schwannomas (1, 2, 4–8, 10, 12, 13, 17, 19–23, 26–33). Intratumoral hemorrhage of malignant tumors, such as malignant gliomas and metastatic tumors, is not uncommon (3). Hemorrhage from trochlear schwannomas is rare, and only one case was previously reported (33). We report a case of trochlear nerve schwannoma in a 42-year-old man who presented with trochlear nerve palsy and left hemiparesis. This case was the first to be reported in which the diagnosis was made before the intratumoral hemorrhage occurred and in which the intratumoral hemorrhage took place NEUROSURGERY DOI: 10.1227/01.NEU.0000204307.99246.17 www.neurosurgery-online.com before the operation. The previous reports are reviewed, and the clinical presentations including the surgical approach and the mechanism of intratumoral hemorrhage are discussed. CASE REPORT A 42-year-old man was admitted to our hospital with left hemiparesis that had appeared 2 weeks previously. Magnetic resonance imaging (MRI) revealed an abnormal lesion beside the brainstem. On examination, the patient was noted to have left hemiparesis (manual muscle test 4/5). A cranial nerve examination showed right trochlear nerve palsy and hypesthesia in the area of the right third division of the trigeminal nerve. A systematic review was normal, and no cutaneous signs of neurofibromatosis were evident. MRI revealed an extra-axial mass, hypo-intense on T1-weighted images and hyper-intense on T2 weighted images. T1-weighted gadolinium enhanced MRI revealed a well-circumscribed enhancing multicystic lesion occupying the interpeduncular cistern, compressing the brainstem. The tumor measured 2.5 cm in diameter. The patient was discharged, and an operation was sched- VOLUME 58 | NUMBER 4 | APRIL 2006 | E791 OHBA ET AL. uled 2 months later. One month later, he was readmitted earlier than expected as an emergency case because his left hemiparesis worsened. Cranial nerve examination showed worsened left hemiparesis (manual muscle test 2/5), right oculomotor nerve palsy, right trochlear nerve palsy, hypesthesia in the entire area innervated by the right trigeminal nerve, and right facial palsy. A computerized tomography scan and MRIs revealed hemorrhage within the tumor and the tumor having expanded to 3.0 cm in diameter (Fig. 1). The patient underwent an operation via the anterior transpetrosal approach. A right temporal craniotomy was performed. The temporal dura was elevated from the middle fossa floor, and the greater superficial petrosal nerve was preserved by cutting the periosteal dura adherent to the nerve. The bone of the posteromedial triangle was drilled. The temporal dura and posterior fossa dura were incised, and then the superior petrosal sinus was ligated, and the sinus and tentorial dura were incised. The tumor was located just beneath the tentorial edge, and the trochlear nerve was located as being posteroinferior to the tumor. The tip of the trochlear nerve was fanned out and unified with the tumor. The tumor was found to have originated from the fourth nerve (Fig. 2). The tumor contained cystic parts with xanthochromatic fluid. The tumor was apparently remote from the trigeminal nerve. We could not detect the oculomotor nerve and abducens nerve, which FIGURE 2. Surgical view after right anterior transpetrosal approach. The tumor originates from the trochlear nerve, which shows a fan-like appearance on tumor. were behind the prepontine arachnoid. Because the border between the tumor and the brainstem was apparent and the tumor did not adhere to the major vascular, we could dissect the tumor off the surrounding structures with ease. Gross total removal of the tumor was performed after amputation of the trochlear nerve. Histopathological examination revealed the characteristic appearance of a schwannoma with a palisading pattern. Several hemorrhage areas and thin-walled dilated vessels were seen (Fig. 3). The patient’s postoperative course was uneventful. His hemiparesis improved postoperatively, and he was discharged 1 week after the operation. MRI performed 4 months later revealed no regrowth of the tumor (Fig. 4). The patient has no neurological deficits except for right trochlear nerve palsy. DISCUSSION FIGURE 1. A, computerized tomography scan without contrast enhancement showing low-density mass with high-density area, suggesting intratumoral hemorrhage. B, axial; C, coronal; D, sagittal T1–weighted gadolinium enhanced MRIs showing well-circumscribed enhancing multicystic lesion in the interpeduncular cistern, compressing the brainstem. E791 | VOLUME 58 | NUMBER 4 | APRIL 2006 Schwannomas commonly arise from the vestibular nerve (80–90%) and less commonly from the trigeminal nerve. There have been rare cases originating from motor cranial nerves, and the facial nerve mostly occupies approximately 40% of nonvestibular schwannomas (12, 25). An association of intracranial schwannomas with neurofibromatosis has been reported (6). Schwannomas originating from motor nerves and not associated with neurofibromatosis are extremely rare. A schwannoma originating from the trochlear nerve was first reported in 1976 by King (17), and a total of 35 cases have been reported, including the present case. Twenty-six of them were histologically diagnosed as schwannomas (Table 1). One case was found incidentally at autopsy (12), and the other 25 were diagnosed by surgery (1, 2, 4–8, 10, 13, 17, 19–23, 26–33). Most of these patients were middle aged, with a mean age of 43.9 years (minimum 16 yr, maximum 68 yr). There was no significant difference in sex (male:female ⫽ 12:14), which is different compared with vestibular schwannomas (25). Preoperative paralysis of the trochlear nerve is only seen in 42% of these tumors. Trochlear nerve palsy is correlated to www.neurosurgery-online.com TROCHLEAR NERVE SCHWANNOMA WITH HEMORRHAGE FIGURE 3. Histopathology. A, spindle-shaped tumor cells with nuclear palisading; B, hypervascularity and thin-walled dilated vessels. Hematoxylineosin, original magnification, ⫻40. tumor size. In cases over 30 mm, almost all cases have trochlear nerve palsy. Characteristic symptoms other than diplopia are headache (46%), hemiparesis (46%), facial paresthesia (35%), oculomotor palsy (27%), and ataxia (19%). Feinberg and Newman (9) reported early suspicion of a schwannoma in cases of unilateral trochlear nerve palsies if the palsy was not congenital or of traumatic origin. In almost all of the patients who underwent surgery, total or subtotal removal was performed. In only one case was partial resection performed (4). All patients had a good outcome. The surgical approach to trochlear schwannomas is selected depending on the direction of tumor growth and the surgeon’s preference. Various approaches have been reported. In about half of the cases, the subtemporal transtentorial approach was selected with minor variations. In the remaining cases, other approaches were used such as the lateral suboccipital, pteri- NEUROSURGERY onal, and presigmoid transpetrosal approaches. In only one case was twostaged surgery via the pterional and suboccipital approaches used. In our case, the tumor was removed via the anterior transpetrosal approach. An advantage of this approach might be reduction of the retraction damage on the temporal lobe for overview of the lower margin of the tumor, FIGURE 4. MRI performed after surthrough epidural access, gery showing gross total removal of tumor and decompression of brain stem. and removal of the petrous apex. Trochlear nerve schwannomas were classified by Celli et al. (6) into three groups according to Jefferson’s (14) classification for the trigeminal variety; cisternal, cisternocavernous, and cavernous. Trochlear nerve schwannomas almost always occur in the cisternal position (23/26) and less in the cisternocavernous (2/26) and cavernous positions (1/26). Almost all schwannomas originating from the trochlear nerve occupy the ambient cistern, ventrolateral to the mesencephalon and pons. These tumors are usually located just beneath the tentorium edge, partially adhering to the tentorium, compressing the midbrain medially. The trochlear nerve was usually identified in the posterior or posteroinferior aspect of the tumor. Because of the anatomic location, there is a higher probability for schwannoma that originated from trochlear nerve to enter the interpeduncle cistern than trigeminal nerve schwannoma. This may be one of the reasons why the symptom of hemiparesis occurs more frequently in the trochlear nerve schwannoma. About half of the tumors contained a cystic component. Cranial nerve schwannomas are reported to arise commonly at the point where the axonal covering switches from glial elements to Schwann cells (25). In case of the vestibular nerve, the length of the neuraxis is 8 mm from the brain stem, and most tumors originate near the site of transition within the internal auditory canal (12, 24). However, the above has not been the case in trochlear nerve schwannomas. The nerve junction is 0.6 mm apart from the brainstem (12); however, in only one case was it located on the dorsal surface of the midbrain. In the other 25 cases including our case, these tumors have been located lateral or anterolateral to the cerebral peduncle, away from the transitional zone. In the current report, the duration of the symptoms was long, and this point is the same as in cases of oculomotor or abducent nerve schwannomas (6). However, in our case, the patient’s symptoms rapidly worsened because of intratumoral hemorrhage, which has also been currently reported by Yamamoto et al. (33). Spontaneous intratumoral hemorrhage from intracranial schwannomas was reported in approximately 30 cases (3, 16). VOLUME 58 | NUMBER 4 | APRIL 2006 | E791 OHBA ET AL. TABLE 1. Summary of reported cases of trochlear nerve schwannomaa IVth Series Age/sex Nerve (reference no.) palsy King (17) 55/F Boggan et al. 32/F (5) Ho (12) 58/F Leunda et al. 54/M (19) Symptoms Duration of symptoms No Rt. facial numbness, 1 yr decreased corneal reflex, ataxia, hemibody hypesthesia, headache, mild facial palsy Yes Retro-orbital 2 yr headache, diplopia, rt. facial palsy, lt. hemiparesis, lt. face numbness, anisocoria, gag reflex slightly depressed, ataxia No No Yes Diplopia, headache, 7 mo partial IIIrd palsy Leunda et al. 16/F (19) Yes Diplopia, headache Yamamoto et 37/F al. (33) Yes Sudden onset of 2 wk headache, nausea, vomiting, diplopia No Mild lt. ptosis, mild 6 mo and variable pupillary inequality No Gait and lt. side 1 yr sensory disturbance, lt. face numbness, lt. taste disturbance No Diplopia (transient), lt. 1 mo hemiparesis, ataxia, lt. facial numbness, lt. sensory disturbance No Rt. hemiparesis, 5 mo diplopia, dysarthria, headache, rt. facial weakness Yes Diplopia (caused by lt. ND IIIrd, IVth palsy), rt. hemiparesis Yes Diplopia, ataxia, lt. 12 mo hemiparesis, lt. dysmetria, headache No Lt. sensory disturbance 8 mo and hemiparesis No Headache, lt facial 4 yr numbness, gait disturbance Yes Diplopia, headache, 8 mo numbness of lt. tongue, lt anisocoria, bilateral papilledema Garen et al. (10) 18/F Tokuriki et al. (30) 43/M Murakawa et 23/F al. (22) Maurice56/M Williams (21) Samii and Draf (26) 53/F Celli et al. (6) 51/M Abe et al. (1) 60/M Abe et al. (2) 57/M Jackowski et al. (13) 26/F E791 | VOLUME 58 | NUMBER 4 | APRIL 2006 5 mo Location Size (mm) Operation Residual Follow-up symptom Cisternal 30 ⫻ 40 Subtemporal transtentorial approach Rt. IVth palsy, minimal weakness of rt. leg 18 mo Cisternal 40 Subtemporal transtentorial approach Rt. IVth palsy, absent rt. coronal reflex 8 mo Cisternal Cisternal 3⫻4 35 Autopsy Subtemporal transtentorial approach Subtemporal transtentorial approach Subtemporal transtentorial approach Subtemporal transtentorial approach Subtemporal transtentorial approach Cisternocavernous 45 Cisternal 10 ⫻ 9 ⫻ 7 Cisternal 25 Cisternal ND Cisternal 18 ⫻ 15 Cisternal 20 Cisternal ND Cisternal 40 ⫻ 30 Cisternal Cisternal Cisternal Rt. IVth palsy 1 yr Lt. IVth palsy 6 mo Rt. IVth palsy 5 yr No ND Rt. IVth palsy 1 mo Pterional approach Rt. IVth palsy ND and suboccipital approach (double stage) Lateral suboccipital Lt. IVth palsy, 2 yr approach rt. slight spasticity Pterional approach Lt. IVth palsy ND Subtemporal Rt. IVth palsy transtentorial approach 30 ⫻ 20 ⫻ 20 Lateral suboccipital Rt. IVth palsy approach 30 ⫻ 20 ⫻ 20 Subtemporal Rt. IVth palsy transtentorial approach ND Transtemporal Mild lt. IVth transtentorial palsy approach 5 yr ND 4 mo 6 mo www.neurosurgery-online.com TROCHLEAR NERVE SCHWANNOMA WITH HEMORRHAGE TABLE 1. Continued IVth Series Age/sex Nerve (reference no.) palsy Dolenc and Coscia (7) Beppu et al. (4) Symptoms 68/M No 66/M No Santoreneos et al. (27) 35/F No Nadkarni and Goel (23) Veshchev and Spektor (32) Matsui et al. (20) 48/F No 26/F No 61/M Ture et al. (31) 31/M Yes Diplopia, lt. hemiparesis, dysphagia Yes Diplopia Shenouda et al. (28) 49/M Du et al. (8) 17/F Shenoy and Raja (29) 54/F Ohba (current study) 48/M Yes Headache, ataxia, diplopia, dysphagia, aggressive behavior, memory loss, lt. IIIrd. palsy, papilledema, absent gag reflex No Headache, diplopia, nystagmus, mild lt. ptosis No Headache, lt. hemiparesis, facial palsy, dysarthria, hoarseness, difficulty of swallowing, rt. ptosis Yes Diplopia, lt. hemiparesis, hypesthesia of rt. face, rt. facial palsy, rt. IIIrd palsy a Duration of symptoms Transient diplopia, lt. 2 yr hemiparesis Tinnitus, rt. hearing 5 yr disturbance, diplopia (caused by IVth palsy), vertigo, rt. dysmetria, hypesthesia in lt. V2 Headache, lt. 8 wk hemiparesis, ataxia, rt. facial palsy Pathological laughter, 6 mo decreased rt. corneal reflex Lt. facial burning pain 3 mo Location Size (mm) Operation Residual Follow-up symptom 30 ⫻ 25 ⫻ 25 Lateral suboccipital Improved rt. approach hemiparesis 2⫻2⫻1 Suboccipital Rt IVth palsy approach Cisternal Cisternal Subtemporal Lt. IVth palsy transtentorial approach Subtemporal Rt. IVth palsy transtenttorial approach Pterional approach Lt. IVth palsy 2 mo ND Cisternal ND Cisternal ND Cavernous ND 3 mo Cisternal ND 2 mo Cisternal 20 ⫻ 15 9 mo Cisternocavernous 40 ⫻ 30 3 mo Cisternal 38 ⫻ 29 ⫻ 25 Orbitozygomatic No pterional approach 2 mo Cisternal ND Subtemporal transtentorial approach Lt. 1 yr hemianesthesia 3 wk Cisternal 25 Anterior transpetrosal approach Rt. IVth palsy 4 mo Presigmoid and transpetrosal approach Infratentorial lateral supracerebellar approach Presigmoid combined petrosal approach 23 mo 6 mo 4 mo Rt. IVth palsy ND Lt. IVth palsy ND Lt. IVth palsy, 6 yr lt. deafness ND Rt, right; Lt, left; ND, not described. Despite the fact that the mechanism of hemorrhage from schwannoma is unclear, increased vascularity with dilated and thin-walled vessels in the histological findings seem to be the cause of intratumoral hemorrhage (3, 18). Russell and Rubinstein (25) reported that tumor vessels often show focal sinusoidal dilatation and hyaline thickening of the walls as secondary changes, and these changed vessels may lead to NEUROSURGERY spontaneous thrombosis with consequent necrosis and often hemorrhage. The tumor size seems to be one of the contributing factors of breeding (18). Kasantikul et al. (15) reported that a marked increase in vascularity was found in almost 60% of the schwannomas larger than 2 cm, whereas such condition was found in only 20 to 25% of all schwannomas. Vessel distortion and distention, and weaker stroma support, which VOLUME 58 | NUMBER 4 | APRIL 2006 | E791 OHBA ET AL. occur as tumor grows, may be associated with intratumoral hemorrhage (3, 16, 18). In our case of trochlear nerve schwannoma, these factors may also be associated with intratumoral hemorrhage. As described above, trochlear nerve schwannomas are very rare, but it may be possible to diagnose preoperatively as so with symptoms and radiographic findings. A precise preoperative diagnosis is most important to plan the treatment. Although intratumoral hemorrhage in schwannomas is rare, the tumor may grow rapidly with intratumoral hemorrhage, which should be kept in mind. REFERENCES 1. Abe T, Iwata T, Shimazu M, Iida M, Izumiyama H, Matsumoto K, Mizutani T, Tanaka H, Aruga T: Two cases of trochlear nerve neurinoma [in Japanese]. No Shinkei Geka 22:371–375, 1994. 2. Abe T, Iwata T, Shimazu M, Matsumoto K: Trochlear nerve neurinoma associated with a giant thrombosed dissecting aneurysm of the contralateral vertebral artery. Surg Neurol 42:438–441, 1994. 3. Asari S, Katayama S, Itoh T, Tsuchida S, Furuta T, Ohmoto T: Neurinomas presenting as spontaneous intratumoral hemorrhage. Neurosurgery 31:406– 411, 1992. 4. 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Ture U, Ozduman K, Elmaci I, Pamir MN: Infratentorial lateral supracerebellar approach for trochlear nerve schwannoma. J Clin Neurosci 9:595–598, 2002. 32. Veshchev I, Spektor S: Trochlear nerve neuroma manifested with intractable atypical facial pain: Case report. Neurosurgery 50:889–891, 2002. 33. Yamamoto M, Jimbo M, Ide M, Kubo O: Trochlear neurinoma. Surg Neurol 28:287–290, 1987. COMMENTS O hba et al. report a patient with a trochlear nerve schwannoma that was diagnosed on imaging studies and subsequently hemorrhaged. This appears to be the first reported case of a trochlear nerve schwannoma that hemorrhaged after radiographic diagnosis (a prior reported case was diagnosed at the time of hemorrhage). This case was also the first reported trochlear nerve schwannoma to be removed through an anterior transpetrosal approach. The discussion includes an excellent review of possible factors leading to hemorrhage in schwannomas, including data showing that as schwannomas enlarge, there is a disproportional increase in the vascularity of the tumors. While rare, trochlear nerve schwannomas should remain in the differential for prepontine lesions. Steven D. Chang Stanford, California T he authors present an interesting and well-documented case report of a 42-year-old male patient suffering from a trochlear nerve schwannoma who presented with hemiparesis and trochlear nerve dysfunction. A detailed review of literature with demonstration of the different approaches is added. The strategy to discharge patients with brain stem compression and schedule surgery after 2 months is questioned by the presented case history. Due to intratumoral hemorrhage, the patient’s neurological status deteriorated. Fortunately, the authors were able to completely remove the tumor and the symptoms, besides the trochlear nerve dysfunction, were reversible. This is an excellent result. Still, in case of brainstem compression, neurosurgeons should advise the patient to seek brainstem decompression as soon as possible. Trochlear schwannomas is a very rare lesion. Among a series of more than 3000 intracranial schwannomas, a second trochlear nerve schwannoma was successfully removed recently via a retrosigmoidal approach www.neurosurgery-online.com TROCHLEAR NERVE SCHWANNOMA WITH HEMORRHAGE in the International Neuroscience Institute, Hannover. In this case, a preservation of the trochlear nerve also was not possible. Wolf Lüdemann Madjid Samii Hannover, Germany O hba et al. reported a very rare occurrence of intratumoral hemorrhage in an uncommon case of trochlear nerve schwannoma. The paper is well written, concise, and the literature review is com- NEUROSURGERY plete. The figures illustrated the hemorrhagic neoplasm and the pathological features of the lesion well. I congratulate the authors for the surgical result obtained through an anterior transpetrosal approach with which the senior author has gained international recognized experience. The mechanism of intratumoral hemorrhage in schwannomas remains obscure, and this case report does not add any data on this aspect. Francesco Tomasello Messina, Italy VOLUME 58 | NUMBER 4 | APRIL 2006 | E791