Midline Suboccipital Approach Research Articles

A brief cardiac arrest due to saline irrigation during surgery for infratentorial cerebellar tumor

The posterior fossa is surrounded by bone and tentorium, and an infratentorial brain tumor can compress normal brain structures, thus eliciting various symptoms. Surgery for an infratentorial tumor may stimulate deep brain structures, which can lead to cardiac autonomic responses. We report a brief sinus arrest immediately before dural closure following saline irrigation during removal of a cerebellar tumor. A 38-year-old female patient with no previous medical his tory underwent an elective surgery for resection of an infratentorial cerebellar tumor. The patient was premedicated with glycopyrrolate 0.2 mg and anesthesia was induced with propofol 80 mg and rocuronium 50 mg. Anesthesia was maintained with 50% O2 in air with 1.6-2.2% sevoflurane and infusion of remifentanil (0.1-0.15 μg/kg/min) and rocuronium (4.5-5.0 μg/kg/ min). The patient was placed in the left lateral park-bench posi tion with the head flexed and the midline suboccipital approach was used for the surgery. The tumor was removed successfully and the dura mater was almost closed except for a 2 mm-sized window for saline irrigation. The patient’s vital signs were stable, with blood pressure 110/70 mmHg, heart rate (HR) 68 beats per min (bpm), and peripheral oxygen saturation (SpO2) 100%. The end tidal carbon dioxide partial pressure (ETCO2) was adjusted to around 32 mmHg. Normothermia was maintained at 36.0-36.2 o C using a forced-air patient warming system (Bair Hugger Ⓡ warming unit, Arizant Healthcare, MN, USA). Room temperature saline was used as an irrigation solution and 30 ml of saline was administered in a 30 ml syringe with a 17 G curved needle tip through a small window of the dura mater. Instantly, the patient developed profound bradycardia and sinus arrest. Electrocardiogram rhythm and arterial blood pressure curve showed an 8-second period of sinus arrest followed by sinus bradycardia. Immediately after being informed of the events, the surgeon stopped the irrigation. The HR returned to normal sinus rhythm (65-70 bpm) without any other treatment and the patient experienced no additional events thereafter. The patient was extubated in the intensive care unit on the following day. Her mental status recovered well and vital signs were stable.

Glossopharyngeal Neuralgia Treated with an Endoscopic Assisted Midline Suboccipital Subtonsillar Approach: Technical Note

Glossopharyngeal nerve neuralgia (GPN) is an exceptionally rare skull-based disorder. It is treated similar to other neurovascular conflicts. The approach, however, is debatable, as the caudal cranial nerves and especially the exit zones at the brainstem are barely visible via the retrosigmoid approach. We demonstrate a case of a typical GPN with microsurgical neurovascular decompression according to standard procedures. Continuous electrophysiological monitoring, including motor-evoked potentials of the glossopharyngeal nerve in addition to somatosensory evoked potential (SSEP) monitoring, was set up. In prone position a midline suboccipital osteoplastic craniotomy was performed. Intradurally, an endoscopic-assisted subtonsillar exposure of the lateral recess and the nerve root exit zone of the glossopharyngeal nerve has been chosen. A large compressing branch of the posterior inferior cerebellar artery (PICA) was identified as the cause of the neurovascular conflict and transposed. A midline subtonsillar approach with endoscopic assistance to the lateral brainstem is a straightforward time- and morbidity-sparing procedure.

Foramen Magnum Meningioma: Our Experience in Five Cases

Introduction: Over 2 years, we operated on five patients with FMM. All the patients had angio-MRI to study the relationship between the tumor and the vertebral artery (VA). In one case, (posterior and pure intradural tumor), the tumor was removed via a midline suboccipital approach with craniotomy and C1-C2 laminectomy. In all other cases, meningiomas were posterolateral, with one of these cases having extradural extension. In all cases, VA was surrounded by tumor. We opted for a modified posterolateral approach with inverted L incision and craniotomy and C1-C2 laminectomy without resecting the occipital condyle. The epidural part of the VA was identified and mobilized laterally. Once VA was identified, we opened dura mater and began to remove the tumor.

Tension pneumoventricle after resection of a fourth ventricle choroid plexus papilloma: An unusual postoperative complication

Background:Pneumocephalus is defined as the presence of air within the intracranial vault. A common complication of head trauma and surgery, pneumocephalus is usually related to ventricular shunts, craniotomies, and surgery in the sitting position. Tension (symptomatic) pneumoventricle is a rare entity associated with significant clinical morbidity.Case Description:We report an unusual case of a 15-year-old girl with tension pneumoventricle developed shortly after removal of a choroid plexus papilloma of the fourth ventricle by a midline suboccipital approach while in the sitting position.Conclusion:The presence of a cerebrospinal fluid (CSF) diversion system that causes a decrease in intracranial pressure and the existence of a craniodural defect with or without an obvious CSF leak may be the cause of tension pneumoventricule. According to our present understanding, this is the first report of this peculiar complication of fourth ventricular surgery. We discuss clinical manifestations, surgical management, contributing factors, and mechanisms involved in the pathogenesis of tension pneumoventricle.

Limited vertical dural opening for lesions of the vermis, 4thventricle, and distal PICA segments

Background:Lesions of the vermis and 4th ventricle are commonly addressed through a midline suboccipital approach. Most neurosurgeons use either a Y-shaped or a curvilinear dural opening in this setting. Although these approaches offer a wide intraoperative surgical exposure, in occasion, the dural opening is difficult to repair primarily, often necessitating the use of a patch, which may increase the risk for development of CSF fistula. We are describing our experience with a limited, vertical, midline, dural opening for approaches to the vermis, tentorium, 4th ventricle, and distal posterior-inferior cerebellar artery (PICA) segments as an alternative to the classic Y-shaped or curvilinear incision.Methods:We report our experience with a limited vertical midline durotomy in five patients with posterior fossa lesions. The lesions treated included a PICA dissecting aneurysm, three metastatic lesions (located in the vermian, floor of the 4th ventricle, and undersurface of the tentorium cerebelli), and one intra-axial tumor (ependymoma). All patients were positioned prone, and the lesions were accessed without difficulty through a limited, vertical, midline durotomy.Results:Mass lesions and vascular abnormalities located from the midline as far lateral as the outlet foramina of the 4th ventricle can be accessed comfortably via a limited midline dural opening when combined with microsurgical techniques, and the use of a frameless Stealth Station Neuronavigation System (SSNS) [Medtronic Sofamor Danek, Inc., Memphis, TN]. By doing this, simple primary dural closure was achieved with a single running absorbable suture without tension in each case.Conclusion:In our experience, a suboccipital linear dural opening appears to be as effective as the more traditional Y-shaped incision, yet allows for quicker and easier primary dural repair.

Traumatic Hemorrhage within a Cerebellar Dermoid Cyst

Intracranial dermoid cysts with hemorrhage are fairly rare. Herein, we reported a 28-year-old female patient with a cerebellar dermoid cyst, which was found accidently on neuro-imaging after head trauma. MR scanning revealed that the lesion was located within the cerebellar vermis and was measured 3.5cm×3.9cm×3.0cm, with hyper-intensity on T1WI and hypo-intensity on T2WI. However, on CT imaging, it showed hyper-dense signals. It was removed completely via midline sub-occipital approach under surgical microscope. Histological examination proved it was a dermoid cyst with internal hemorrhage. In combination with literature review, we discussed the factors that might be responsible for the hemorrhage within dermoid cysts.

Cavernous Malformations: A Paradigm for Progress

Cavernous Malformations: A Paradigm for Progress

Abscess of the Medulla Oblongata in a Toddler: Case Report and Technical Considerations Based on Magnetic Resonance Imaging Tractography

We report a unique case of a toddler (the only one reported) successfully operated on for a medulla oblongata abscess and comment on the influence of neuroimaging modalities in the preoperative planning of the surgical approach. We report a case of a 20-month-old child with a solitary medulla oblongata abscess. The abscess appeared to be in close proximity to the anterior medulla oblongata, but preoperative planning based on diffusion tensor imaging (DTI) tractography motivated us to try to remove this lesion through a midline suboccipital approach. The ventral medulla oblongata abscess was surgically removed via a telovelar approach. At the anterior wall of the 4th ventricle, a fenestration was made with pus release and evacuation of the cavity. The child was discharged 1 week later with an uneventful and full recovery. Modern imaging modalities of the nervous system can be very helpful in preoperative planning. Functional visualization of the nervous system provided by modern imaging techniques, such as the DTI tractography, can alter the classic topographic concept of surgical approach. In the case presented, approaching an anterior medulla oblongata abscess based on DTI tractography data, through a suboccipital midline transventricular approach, proved to be an effective and safe technique.

Possible Neuro-Sweet Disease Mimicking Brain Tumor in the Medulla Oblongata -Case Report-

A 62-year-old male presented with a rare case of possible neuro-Sweet Disease (NSD) mimicking brain tumor in the medulla oblongata, manifesting as numbness in the bilateral upper and lower extremities, gait disturbance, dysarthria, and swallowing disturbance which gradually deteriorated over 3 months. Magnetic resonance imaging showed a mass lesion in the medulla oblongata, extending to the upper cervical cord with rim enhancement by gadolinium. The preoperative diagnosis was brain tumor, such as glioma, or inflammatory disease. His neurological symptoms gradually deteriorated, so biopsy was performed through the midline suboccipital approach. Histological examination showed infiltration of inflammatory cells, mainly lymphocytes and macrophages. Human leukocyte antigen typing showed Cw1 and B54 which strongly suggested possible NSD. Steroid pulse therapy was started after surgery and the clinical symptoms improved. Neurosurgeons should be aware of inflammatory disorders such as NSD mimicking brain tumor.

Congenital Cleft of Anterior Arch and Partial Aplasia of the Posterior Arch of the C1

Congenital anomalies in arches of the atlas are rare, and are usually discovered incidentally. However, a very rare subgroup of patients with unique radiographic features is predisposed to transient quadriparesis after minor cervical or head trauma. A 46-year-old male presented with a 2-month history of tremor and hyperesthesia of the lower extremities after experiencing a minor head trauma. He said that he had been quadriplegic for about 2 weeks after that trauma. Radiographs of his cervical spine revealed bilateral bony defects of the lateral aspects of the posterior arch of C1 and a midline cleft within the anterior arch of the atlas. A magnetic resonance imaging revealed an increased cord signal at the C2 level on the T2-weighted sagittal image. A posterior, suboccipital midline approach for excision of the remnant posterior tubercle was performed. The patient showed significant improvement of his motor and sensory functions. Since major neurologic deficits can be produced by a minor trauma, it is crucial to recognize this anomaly.

Surgical management of large solid hemangioblastomas of the posterior fossa

From January 2000 to January 2009, 15 patients presented with large solid hemangioblastomas of the posterior fossa; eight of these patients were also diagnosed with von Hippel-Lindau (VHL) disease. Diagnostic imaging showed large vascular lesions. All 15 patients underwent surgery through a suboccipital ipsilateral, modified far-lateral, suboccipital midline or suboccipital supracerebellar approach. Preoperative embolization was attempted in seven patients. Complete removal of the tumor was performed in all patients. An overall neurological improvement was observed in 11 of the 15 patients, corresponding to 61.5%. During follow-up, six patients, all with VHL disease, developed recurrence. Two patients died of renal cell carcinoma after 1 year. Our favorable outcomes suggest that surgical resection is the optimal treatment for patients with large solid hemangioblastomas of the posterior fossa. With improved microsurgical techniques and a better understanding of the vascular pattern of this type of tumor, total microsurgical removal can be performed with low mortality.

Large Cystic Hypoglossal Schwannoma with Fluid-Fluid Level: A Case Report

Hypoglossal schwannomas are rare skull base tumors. Furthermore, cystic hypoglossal schwannomas are extremely uncommon. We report the first case of a large cystic hypoglossal schwannoma with a fluid-fluid level. A 36-year-old woman presented with increased intracranial pressure and cerebellar signs without hypoglossal nerve palsy. Magnetic resonance imaging showed a predominantly cystic mass with a fluid-fluid level in the foramen magnum region extending into the hypoglossal canal. The intracranial tumor was largely removed via a midline suboccipital subtonsillar approach, leaving only a tiny residue in the hypoglossal canal. Histology confirmed a schwannoma with relative hypervascularity. Twenty months later, the tumor recurred and presented as a multicystic dumbbell-shaped lesion, extending intra- and extracranially through the enlarged hypoglossal canal. A complete resection of the intracranial and intracanalicular parts of the tumor was achieved with a small extracranial remnant treated by radiosurgery. Histology revealed a focal increased K(i)67 proliferative index. In this report, we discuss the possible reasons for the absence of hypoglossal nerve palsy and the potential mechanism of the formation of the fluid-fluid level, and we consider the treatment of this lesion.

Tailored Surgical Approaches for Benign Craniovertebral Junction Tumors

We report our surgical experience in the treatment of 16 consecutive patients with benign craniovertebral junction (CVJ) tumor, observed from 2003 to 2008 at our department. We had treated 6 foramen magnum meningiomas, 6 cervicomedullary hemangioblastomas, 1 accessory nerve schwannoma, 1 hypoglossal nerve schwannoma, 1 C2 root schwannoma, and 1 cavernous hemangioma. Clinical results were evaluated by Karnofsky Performance Scale (KPS) and all patients underwent preoperative neuroradiological evaluation with computed tomography (CT) and magnetic resonance image (MRI). Angiography was performed in 15 patients and preoperative embolization was done in 2 patients. Five far-lateral, 1 supracondylar and 10 midline suboccipital approaches were performed. Gross total removal was achieved in 15 cases (94%) and subtotal removal in 1 patient (6%). None of the patients required occipitocervical fusion. Radiological follow-up showed no recurrence in cases totally removed. Postoperative decrease of KPS scores was recorded in only 1 patient. The treatment of cervicomedullary solid hemangioblastoma presented particular issues : by preoperative embolization, we removed tumor totally without an excessive bleeding or brainstem injury. In one of foramen magnum meningioma, we carried out subtotal removal due to hard tumor consistency and encasement of neurovascular structures. : The choice of surgical approaches and the extent of bone resection should be defined according to the location and size of individual tumors. Moreover, we emphasize that preoperative neuroradiological evaluations on presumptive tumor type could be helpful to the surgeon in tailoring the technique and providing the required exposure for different lesions, without unnecessary surgical steps.

Trans-cerebellomedullary fissure approach with special reference to lateral route

The trans-cerebellomedullary fissure (CMF) approach provides good exposure of the fourth ventricle without splitting the inferior vermis. The popularly utilized trans-CMF approach is performed in the midline suboccipital approach. However, the trans-CMF approach actually has two routes: medial and lateral. The lateral route is the trans-CMF approach through a lateral foramen magnum approach such as the transcondylar approach, opening the CMF from the lower unilateral side. We studied the surgical anatomy of the CMF and fourth ventricle. Based on the anatomic findings, we adopted the lateral route of the trans-CMF approach for four patients, each with a tumor near the jugular tubercle extending into the fourth ventricle through the CMF. Our study demonstrated that the lateral route of the trans-CMF approach enables sufficient exposure of not only unilateral cerebellopontine cistern but also of the lateral part of the fourth ventricle. A tumor is safely removed by this approach with easy feeder or tumor bed controls, especially if it is anchored at the lateral part of the CMF as is the jugular tubercle meningioma.

Foramen magnum meningioma originating from the dentate ligament

The authors report a woman with a foramen magnum meningioma originating from the dentate ligament. A 72 year-old woman developed posterior neck pain and a tingling sensation in the left arm. Magnetic resonance imaging showed a well defined and homogenously enhancing mass at the foramen magnum with no dural attachment. Angiography did not demonstrate a blood supply to the tumour via the posterior meningeal branches of the vertebral artery. The mass was totally removed via a midline suboccipital approach. Intraoperatively, the mass was found to adhere to the dentate ligament without a dural attachment. Histopathology findings were consistent with the diagnosis of meningioma. This case is the first report of a meningioma originating from the dentate ligament and the tumour may have originated from the pia-arachnoidal extension of the spinal cord to the dura.

Surgical treatment for posterior inferior cerebellar artery aneurysms

Objective To explore the clinical characteristics and surgical managements of posterior inferior cerebellar artery (PICA) aneurysms. Methods Retrospective analysis of the clinical features, imaging characteristics and clipping results of 21 PICA artery aneurysms. This series included 9 men and 12 women, mean age was 40.6 years. One presented with mass pressure effects of infrotentoria fossa; 20 patients presented with severe and sudden onset of symptoms, reflecting a hemorrhage from a PICA aneurysm. Hunt-Hess and Hess grades at presentation were: Grade Ⅰ in 1 patient, Grade Ⅱ in 14 patients, Grade Ⅲ in 5 patients, Grade Ⅳ in 1 patient. The bleeding was confined to the infrotentoria subarachnoid space (SAH) and/or the fourth ventricle. Arteriographies revealed 13 proximal PICA aneurysms and 8 distal PICA aneurysms. Results Lateral suboccipital and midline suboccipital surgical approaches were used to secure the aneurysms in all patients, either by direct clipping in 19 cases, parent artery's occlusion in 1 case and parent artery's sacrifice in 1 case. Transient CSF leak occurred in 3 patents; paresis and lower cranial nerve dysfunction and long-term coma occurred in 1 patient; mild lower cranial nerve dysfunctions occurred in 2 patients, and had good recovery at 3 months of follow-up; no complication in other patients. Conclusions The favorable outcomes and low postoperative morbidity in our patients argues that surgical clipping be considered a first-line therapeutic option. The protection of the low cranial nerves and the preservations of PICA are major contributors to good long-term results. Key words: Posteroinferior cerebellar artery; Aneurysm clipping; Subarachnoid hemorrhage

Intra-axial Brainstem Malignant Melanoma Mimicking Cavernous Angioma -Case Report-

A 41-year-old female presented with repeated pontine hemorrhage. Magnetic resonance imaging showed the pontine hemorrhage as a heterogeneously enhanced mass mimicking cavernous angioma. The mass lesion was removed via a midline suboccipital approach. Histological examination showed malignant melanoma cells. No cutaneous lesion was found and positron emission tomography found no abnormalities. Our presumptive diagnosis was primary intra-axial brainstem malignant melanoma. The possibility of malignant melanoma should be considered in patients with intra-axial brainstem lesion associated with repeated hemorrhages.

脳幹部海綿状血管腫に対する治療戦略 脳幹部海綿状血管腫に対する手術手技―自験例よりｍｉｄｌｉｎｅ ｓｕｂｏｃｃｉｐｉｔａｌ ａｐｐｒｏａｃｈの検討―

We reviewed the cases of brain stem cavernous malformation treated at Kyoto University Hospital between 1983 and 2007. We employed a midline suboccipital approach in 15 cases of a total 21 cases. Here we describe the pitfalls of this approach at our institute.

Outcomes of Surgical Resection of Large Solitary Hemangioblastomas of the Craniocervical Junction with Limitations in Preoperative Angiographic Intervention: Report of Three Cases

Hemangioblastomas of the central nervous system may occur sporadically, or in association with von Hippel-Lindau (vHL) disease. The treatment of large solitary hemangioblastomas of the posterior cranial fossa mandates a combination of angiographic intervention and surgery. However, large tumors may derive their vascularity from major cerebellar vessels, which can make their embolization hazardous. To describe the surgical outcomes of three cases of large hemangioblastomas with compression of the medulla oblongata, where the potential for preoperative embolization was extremely limited. Three patients (all males; 68, 36 and 38 years) presented with a history of chronic headache and caudal cranial nerve deficiencies. Diagnostic imaging showed large vascular lesions (4 x 3, 4 x 5 and 5 x 5 cm) at the craniocervical junction, compressing the brainstem. There were no concomitant findings associated with vHL disease. Staged treatment was administered. Preoperative embolization was attempted at first. One patient (68 yrs) showed a PICA occlusion and associated cerebellar infarction after embolization; embolization was deemed hazardous in the other two. In the second phase, the lesions were removed via a midline suboccipital approach with resection of the arch of altas. Complete removal was possible in all three cases. POSTOPERATIVE COURSE AND FOLLOW-UP: The caudal cranial nerve deficiencies deteriorated soon after surgery in all three patients. A tracheotomy was required in two patients, which was removed uneventfully during the rehabilitation phase. Ventriculo-peritoneal shunts were implanted in two patients. MRI follow-up three (1 case) and four years (2 cases) after surgery showed no relapse. The Karnofsky Index scores were 80, 70 and 90 in the three patients aged 68, 36 and 38, respectively. Total microneurosurgical removal of large hemangioblastomas at the craniocervical junction with limited preoperative embolization (associated with morbidity) should be seriously considered. Although the early outcome is not encouraging, the long-term outcomes seem favorable.

Large cystic cavernous angioma of the cerebellum mimicking pilocytic astrocytoma

Cavernous angiomas are relatively rare vascular malformations. They are generally located supratentorially with a rare incidence in the cerebellum. Cavernous angiomas, accompanied by a large cyst, are very rare. We present a case of a cavernous angioma with the unusual MRI findings of a large cyst and a small mural nodule. The patient was a 48-year-old man who complained of a history of dizziness for several weeks. The neurologic examination in the neurosurgery clinic was without deficit. The cyst measured 4.7x4.0 cm and contained serous fluid with a nodular mass in the lower part of the cyst. The cystic wall and the solid mural nodule were completely removed through a midline suboccipital approach. Postoperatively, the patient remained neurologically intact. When a large cystic lesion is present in the cerebellum, preoperative radiological and intraoperative findings led to misdiagnosis. Therefore, a rare cystic angioma must be considered in the differential diagnosis of infratentorial cystic masses.