Endoscope-assisted retrosigmoid intradural suprameatal approach to the middle fossa: anatomical and surgical considerations.

INTRODUCTION: Lesions involving the posterior and middle fossa may be reached by several surgical approaches depending mostly on tumors' location and characteristics. The retrosigmoid intradural suprameatal approach has been used to remove tumors of the posterior fossa extending into Meckel's cave and the middle fossa. With large tumors, this approach may allow exposure of the oculomotor and optic nerves, the supraclinoid internal carotid and communicating posterior arteries. METHODS: Three formaldehyde-fixed specimens have been prepared on both sides using the conventional retrosigmoidal-suprameatal approach. The entire endoscopic preparations have been documented via a digital recording system, using a 5mm endoscope with a 25 degrees perspective. The authors describe the anatomical corridor and technique of the endoscope-assisted retrosigmoid intradural suprameatal approach to lesions that are located predominantly within the posterior fossa and supratentorial extension into Meckel's cave, sellar and parasellar region. CONCLUSIONS: The endoscope-assisted suprameatal approach provides exposure of the antero-medial middle fossa even in cases of skull base lesions that have not caused significant displacement of neurovascular structures.

Peduncular hallucinosis after sacrifice of veins of the petrosal venous complex for trigeminal neuralgia.

Peduncular hallucinosis is characterized by striking visual images, highly colored and mobile, which are recognized by the patient as imaginary. A 50-year-old-man underwent microvascular decompression for a classical right sided trigeminal neuralgia. During the procedure, the petrosal vein and a transverse pontine vein were sacrificed for trigeminal decompression. On the second postoperative day, the patient developed peduncular hallucinosis that disappeared on the forth postoperative day. This is the third case in the literature of peduncular hallucinosis after obliteration of veins of the petrosal venous complex for trigeminal neuralgia. The best policy in cerebellopontine angle surgery is to preserve the petrosal vein whenever possible to avoid complications related to venous congestion.

Acute subdural haematoma without subarachnoid haemorrhage caused by rupture of an internal carotid artery bifurcation aneurysm: case report and review of literature.

Spontaneous pure acute subdural haematoma (ASDH) without intraparenchymal or subarachnoid haemorrhage caused by a ruptured cerebral aneurysm is extremely rare. To our knowledge, the present case is the first report of an internal carotid artery bifurcation aneurysm presenting as pure ASDH. Suitable diagnostic investigations and therapeutic strategies are discussed. Arterial origin of bleeding should be considered in all cases of non-traumatic ASDH and a vascular anomaly has to be excluded. The neurological status on admission dictates the appropriate timing and methodology of the neuroradiological investigations.

Rosai-Dorfman disease involving the cranial base, paranasal sinuses and spinal cord.

Rosai-Dorfman disease is a lymphoproliferative disease that rarely involves the central nervous system. A 32-year-old patient with an extensive process involving the petroclival region, cavernous sinuses, suprasellar region, anterior cranial fossa, paranasal sinuses, nasal cavity and spinal cord is reported. Sinus histiocytosis with massive lymphadenopathy lesions may be dural-based and located in the skull base. As these lesions may clinically and radiologically mimic meningiomas as well as other disorders, Rosai-Dorfman disease should be included in the differential diagnosis of extensive lesions involving the intracranial and spinal compartments along with meningiomatosis and inflammatory diseases. The individual management of Rosai-Dorfman disease may be challenging due to diffuse involvement of neurovascular structures at the skull base.

Trigeminocardiac reflex during skull base surgery: mechanism and management.

BACKGROUND: We study the occurrence and management of the trigeminocardiac reflex (TCR) during neurosurgical procedures for lesions of the skull base. METHOD: Two hundred patients underwent neurosurgical procedures for various skull base lesions and were evaluated retrospectively for the occurrence of the TCR during surgery. This phenomenon was defined as the onset of bradycardia lower than 60 beats/minute and hypotension with a drop in mean arterial blood pressure of 20% or more due to intra-operative manipulation or traction on the trigeminal nerve. FINDINGS: Sixteen patients (8%) had a TCR intra-operatively (7 vestibular schwannomas, 5 sphenoid wing meningiomas, 3 petroclival meningiomas, 1 intracavernous epidermoid cyst). In all 16 patients with a TCR the postoperative courses presented no complications that could be directly related to this intra-operative phenomenon. CONCLUSIONS: Due to the intracranial course of the trigeminal nerve several surgical procedures at the anterior, middle and posterior skull base may elicit the trigeminocardiac reflex. Continuous monitoring of hemodynamic parameters allows the surgeon to interrupt surgical manoeuvres immediately upon the occurrence of the TCR. This technique is sufficient for the heart rate and the arterial blood pressure to return to normal levels without the necessity of additional anticholinergic medication.

[Epidural spinal cavernous angioma: case report]. / Angioma cavernoso espinhal epidural: relato de caso.

Epidural spinal cavernous angiomas account for approximately 4% of all spinal epidural tumors. More recently the diagnosis has become more frequent due to refinement of imaging modalities. We describe a 50-year-old woman with a spinal epidural cavernous angioma at L1-L2, which was successfully surgical treated. Clinical picture, imaginology and treatment of this entity is reviewed.

[Internal carotid bilateral occlusion, meningovascular syphilis and AIDS: case report]. / Oclusão bilateral das artérias carótidas internas, sífilis meningovascular e SIDA. Relato de caso.

We report a case of bilateral occlusion of internal carotid arteries, presenting with right hemiparesis and hypoesthesia, associated to meningovascular syphilis in a patient with AIDS. CT scan showed few small hypodense lesions, with a predominance on the left side, and the angiography showed bilateral occlusion of the carotid arteries. The association between syphilis and AIDS is not unusual, but the paucity of symptoms, probably due to a slow and gradual occlusion is not commonly reported.

The retrosigmoid intradural suprameatal approach to posterior cavernous sinus: microsurgical anatomy.

OBJECTIVE: The retrosigmoid intradural suprameatal approach includes the standard retrosigmoid suboccipital route with drilling of the petrous bone above and anterior of the internal auditory meatus, allowing for exposure of the trigeminal nerve within the Meckel's cave and of the middle fossa. In this study, the authors analyzed the potential use of an extended variation of the suprameatal route to approach the posterior cavernous sinus for microsurgery of, e.g., petroclival meningiomas and trigeminal schwannomas. METHODS: The microsurgical anatomy of the retrosigmoid suprameatal approach was examined by using 10 adult cadaveric specimens (20 sides), using 3-40x magnification. The exposure to the posterior cavernous sinus provided by this approach was focused. RESULTS: After drilling the suprameatal tubercle toward the petrous apex, the Meckel's cave was exposed. The trochlear nerve was the landmark for opening the cavernous sinus by this approach. The dura located medially to the entry point of the trochlear nerve into the tentorium was resected, allowing exposure of the intracavernous carotid artery with its meningohypophyseal trunk. CONCLUSION: The extended retrosigmoid intradural suprameatal approach allows exposure of the posterior cavernous sinus and may be used to remove lesions of the posterior fossa extending into the Meckel's cave and into the cavernous sinus.

Venous complications following petrosal vein sectioning in surgery of petrous apex meningiomas.

OBJECTIVE: Meningiomas involving the petrous apex regularly show a close relationship with the superior petrosal vein which is sometimes obliterated during surgery due to its proximity to the tumour. However, there is no study available so far focusing on the frequency of postoperative venous congestion related complications following petrosal vein obliteration as well as on pre- and intraoperative findings related to them. METHODS: Fifty-nine patients with meningiomas involving the petrous apex were analyzed concerning the intraoperative preservation or sacrifice of the petrosal vein and postoperative complications related to venous occlusion. RESULTS: When a petrosal vein was occluded, in 9 of 30 cases venous-related complications occurred with a minor venous-congestion phenomenon in seven cases and major complications in two cases. When the petrosal vein complex was preserved, there were no similar complications. CONCLUSION: Preservation of the petrosal venous complex, especially of large caliber veins, should be attempted whenever possible to increase the safety of surgery. In cases of petrosal vein obliteration, effective brainstem decompression following tumour removal is essential to minimizing the risk of cerebellar congestion.

Petrosal vein occlusion in cerebello-pontine angle tumour surgery: an anatomical study of alternative draining pathways.

OBJECTIVE: The present anatomic study investigates alternative draining pathways of the petrosal vein territory, which allow compensation in case of surgical sacrifice. METHODS: In eight (four formaldehyde fixed and four alcohol fixed) specimens the petrosal vein complex has been dissected and studied. Three heads have been selectively injected via the superior petrous sinus with colored silicon in two different colors. Thereafter the posterior fossa content was removed epidurally from the skull and further fixed in 4% formaldehyde. The nervous and vascular structures were dissected under microscopic control, measured and photographed. 3D-photographs were elaborated. RESULTS: The petrosal vein was present in all cases and joined the superior petrous sinus always lateral to the trigeminal nerve as a single trunk. In the selectively injected specimens no passage of the colored silicon mixture to the contralateral venous brainstem territory could be discerned. However, the ipsilateral anastomoses to the deep supratentorial venous system--peduncular, anterolateral pontomesencephalic, lateral mesencephalic veins, and the tectal veins in connection with the pontotrigeminal vein--filled in all cases. CONCLUSION: Although the present anatomical model does not reflect physiological aspects of vascular dynamics, we document an apparently compensatory venous blood drainage occurring via anastomotic pathways directed to the ipsilateral supratentorial venous system. These findings represent an interesting aspect for preoperative image-guided planning in cerebello-pontine angle surgery.

Image-guided craniotomy for frontal sinus preservation during meningioma surgery.

OBJECTIVE: Preservation of the frontal sinus (FS) during the frontolateral approach to the skull base reduces morbidity, enhances patient comfort, and speeds up the surgical procedure. Due to its irregular outline, mental reconstruction of the borders of FS from two-dimensional images is challenging during surgery. This study was designed to evaluate the impact of neuronavigation on identification and preservation of the FS during frontolateral craniotomies. METHODS: Forty-five patients with pathologies located in the anterior skull base and in the parasellar region were included. A standard computed tomography (CT) sequence was obtained from each patient and uploaded onto an image-guidance system for volumetric rendering of 3D images. The outline of the FS was visualized and the distance between its lateral border and the mid-pupillary line (MPL) was measured. The results were used for navigated craniotomies and compared to the intra-operative findings. RESULTS: The FS was located medial, on and lateral to the MPL in 32, 4 and 9 cases, respectively. The individual outline of the FS could be identified with a mean target registration error of 1.4mm (+/-0.7 mm). The craniotomy could be custom-tailored for each patient according to the individualized landmarks while visualizing the lesion and the surgical landmarks simultaneously. Unintended opening of the frontal sinus or orbit did not occur in any of these cases. CONCLUSION: Image-guided craniotomies based on 3D volumetric image rendering allow for fast and reliable demarcation of complex anatomical structures hidden from direct view in frontolateral approaches. The outline of the frontal sinus and the orbit can be appraised at a glance providing additional safety and precision during craniotomy.

Surgical planning for retrosigmoid craniotomies improved by 3D computed tomography venography.

OBJECTIVE: It is impossible to precisely anticipate the crooked course of the transverse and sigmoid sinuses and their individual relationship to superficial landmarks such as the asterion during retrosigmoid approaches. This study was designed to evaluate this anatomical relationship with the help of a surgical planning system and to analyze the impact of these in vivo findings on trepanation placement in retrosigmoid craniotomies. METHODS: In a consecutive series of 123 patients with pathologies located in the cerebellopontine angle, 72 patients underwent surgical planning for retrosigmoid craniotomies based on 3D volumetric renderings of computed tomography venography. By opacity modulation of surfaces in 3D images the position of the asterion was assessed in relationship to the transverse-sigmoid sinus transition (TST) and compared to its intraoperative localization. We evaluated the impact of this additional information on trepanation placement. RESULTS: The spatial relationship of the asterion and the underlying TST complex could be identified and recorded in 66 out of 72 cases. In the remaining 6 cases the sutures were ossified and not visible in the 3D CT reconstructions. The asterion was located on top of the TST in 51 cases, above the TST in 4 cases, and below the TST in 11 cases. The location of the trepanation was modified in 27 cases due to the preoperative imaging findings with major and minor modifications in 10 and 17 cases, respectively. CONCLUSION: Volume-rendered images provide reliable 3D visualization of complex and hidden anatomical structures in the posterior fossa and thereby increase the precision in retrosigmoid approaches.

The midline suboccipital subtonsillar approach to the hypoglossal canal: surgical anatomy and clinical application.

Primary lesions of the hypoglossal canal, such as hypoglossal schwannomas, are rare. No consensus exists with regard to the surgical approach of choice for treatment of these lesions. Usually, lateral transcondylar approaches have been used. The authors describe the surgical anatomy of the midline subtonsillar approach to the hypoglossal canal. This approach includes a midline suboccipital craniotomy, dorsal opening of the foramen magnum and elevation of ipsilateral cerebellar tonsil to expose the hypoglossal nerve and its canal. The midline subtonsillar approach permits a straight primary intradural view to the hypoglossal canal. There is no necessity of condylar resections. The surgical anatomy of the subtonsillar approach is described and illustrated by an example of a case.

Atypical teratoid-rhabdoid tumor spreading along the trigeminal nerve.

We here describe the case of a boy with an atypical teratoid-rhabdoid tumor (ATRT) of the 4th ventricle at 1 year of age and a local tumor recurrence at 19 months of age. Due to brainstem infiltration, only incomplete tumor resection was possible each time. High-dose chemotherapy, stem cell transplantation and irradiation resulted in complete tumor remission on a control MRI. At 8 years of age, another tumor appeared extending from the cerebellopontine angle along the right trigeminal nerve through Meckel's cave into the cavernous sinus. The trigeminal tumor was not in continuity with the primary ATRT but was located within the field of prior irradiation, neuroradiologically mimicking a schwannoma or a meningioma. The origin of the trigeminal tumor as a late metastasis of the former ATRT or as a less likely irradiation-induced secondary ATRT and the operative approach are discussed.

Meningioma of the accessory nerve extending from the jugular foramen into the parapharyngeal space.

A 35-year-old man presented with pain in the right shoulder and neck for 18 months. The neurological examination revealed complete accessory nerve palsy on the right side without further deficits. Magnetic resonance imaging showed a right parapharyngeal tumour expanding into the posterior fossa through the jugular foramen without dural attachment and absence of invasion into the middle ear cavity or internal auditory meatus. Intraoperative inspection disclosed a tumour originating from the accessory nerve. Histological diagnosis revealed a meningothelial meningioma with invasion of the epineural space. To the knowledge of the authors this is the first report of an accessory nerve meningioma in the jugular foramen associated with a posterior fossa component and extension into the parapharyngeal space.

Ventral extradural spinal meningeal cyst causing cord compression: neurosurgical treatment

Spinal extradural meningeal cysts are typically formed by a thin fibrotic membranous capsule, macroscopically similar that of an arachnoid membrane, filled by cerebro spinal fluid and related to a nerve root or to the posterior midline. Ventral location is extremely rare and when it occurs they usually cause spinal cord herniation through the ventral dural gap. A 61 year-old man who began with a two years long history of insidious tetraparesis, spasticity and hyperreflexia in lower extremities, and flaccid atrophy of upper limbs, without sensory manifestations, is presented. Investigation through magnetic resonance imaging demonstrated an extensive spinal ventral extradural cystic collection from C6 to T11. The lesion was approached through a laminectomy and a cyst-peritoneal shunt was introduced. The cyst reduced in size significantly and the patient is asymptomatic over a 48 months follow-up. This is the first reported case of a spontaneous ventral extradural spinal meningeal cyst causing cord compression. Cyst-peritoneal shunt was effective in the treatment of the case and it should be considered in cases in which complete resection of the cyst is made more difficult or risky by the need of more aggressive surgical maneuvers.

Cistos meníngeos extradurais espinhais são formados tipicamente por estreita cápsula membranosa fibrótica, macroscopicamente semelhante a uma membrana de aracnóide, repleta de líquor e relacionada com uma raiz nervosa ou com a linha média posterior. Eles são extremamente raros em posição anterior e, quando ocorrem, habitualmente causam herniação da medula espinhal pela falha dural ventral. O caso de um homem de 61 anos de idade que iniciou com tetraparesia, espasticidade e hiperreflexia em membros inferiores, e flacidez com hipotrofia nos membros superiores, sem manifestação sensitiva, é apresentado. A investigação com ressonância magnética demonstrou extensa coleção cística extradural ventral à medula de C6 a T11. A lesão foi abordada diretamente via laminectomia com introdução de derivação cisto-peritoneal, reduzindo o cisto e tornando o paciente assintomático com um seguimento de 48 meses. Este é o primeiro caso relatado de cisto meníngeo extradural ventral espontâneo causando compressão medular. A derivação cisto-peritoneal se mostrou eficaz no tratamento do caso e deve ser considerada em situações em que a ressecção completa do cisto esteja impossibilitada, ou dificultada pela necessidade de manobras cirúrgicas mais agressivas e arriscadas.