Anatomical considerations and surgical manipulation of the rhomboid lip in microvascular decompression for hemifacial spasm.

BACKGROUND: In microvascular decompression (MVD) procedures for hemifacial spasm (HFS), surgeons often encounter a rhomboid lip which may obscure the root exit zone (REZ) of the facial nerve. This study aims to explore the anatomical variations of rhomboid lips and their surgical implications to improve safety and effectiveness in MVD surgeries. METHODS: A retrospective analysis was conducted on 111 patients treated for HFS between April 2021 and March 2023. The presence of a rhomboid lip was assessed through operative video records, and its characteristics, dissection methods, and impact on nerve decompression outcomes were further examined. Preoperative magnetic resonance imaging (MRI) scans were reviewed for detectability of the rhomboid lip. RESULTS: Rhomboid lips were identified in 33% of the patients undergoing MVD, with a higher prevalence in females and predominantly on the left side. Two distinct types of rhomboid lips were observed: membranous and cystic variations. The membranous type was noted for its smaller size and position ventral to the choroid plexus. In contrast, the cystic variation was distinguished by its larger size and a thin membrane that envelops the choroid plexus. Preoperative MRI successfully identified rhomboid lips in only 21% of the patients who were later confirmed to have them in the surgical procedures. Surgical approaches primarily involved incisions on the dorsal wall and along the glossopharyngeal nerve root, with only limited need for extensive dissection from lower cranial nerves. Immediate spasm relief was observed in 97% of the patients. One case exhibited a lower cranial nerve deficit accompanied by brainstem infarction, which was caused by the dissection from the lower cranial nerves. CONCLUSIONS: Recognizing the two variations of the rhomboid lip and understanding their anatomical structures are essential for reducing lower cranial nerve injuries and ensuring effective nerve decompression.

Primary intraosseous cavernous hemangioma of the clivus: A case report and literature review.

Background: The radiographic presentation of the primary intraosseous cavernous hemangiomas (PICHs) is nonspecific. We report a case of clival PICH mimicking a chordoma with a literature review. Case Description: A 57-year-old woman presented with diplopia that started a few days before the presentation. She had transient diplopia at the right lateral gaze and upper gaze with normal eye movement. The symptoms disappeared spontaneously 1 week later. She had no other complaints or neurological deficits. Computed tomography revealed an intraosseous mass lesion and bone erosion of the middle and lower clivus, extending laterally to the right occipital condyle. Magnetic resonance imaging (MRI) showed hyperintense and hypointense components on T2- and T1-weighted images, respectively. The lesion was larger than on MRI performed 10 years earlier. Chordoma or chondroma was considered a possible preoperative diagnosis. An endoscopic transsphenoidal approach removed the tumor. In the operating view, the lesion appeared as "moth-eaten" bony interstices filled with vascular soft tissue. Histologically, an intraosseous cavernous hemangioma was diagnosed. Conclusion: Diagnosis before surgery is difficult without characteristic radiographic findings. When making a differential diagnosis of malignant skull lesions, PICH should be considered.

[Intracranial germinoma associated with Down syndrome: case report and review of literature].

It is well known that Down syndrome is sometimes associated with leukemia. However, there have been only a few case reports of a relationship between Down syndrome and brain tumors. The case was that of a 35-year-old man with Down syndrome complaining of gait disturbance. Computed tomography (CT) and magnetic resonance imaging (MRI) showed a mass lesion in the pineal and bilateral cerebello-pontine cistern and spinal cord, marked hydrocephalus. Endoscopic biopsy and third ventriculostomy was performed. Surgical specimens showed typical germinoma. The patient was treated with a combination of chemotherapy with carboplatin and etposide, and irradiation. However he finally died 35 months after these therapies. Cases of malignant tumors other than leukemia, which are associated with Down syndrome, are extremely rare. We reviewed such rare cases of Down syndrome and intracranial germ cell tumor.

Visualization of Dark Side of Skull Base with Surgical Navigation and Endoscopic Assistance: Extended Petrous Rhomboid and Rhomboid with Maxillary Nerve-Mandibular Nerve Vidian Corridor.

BACKGROUND: Lesions located at the petrous apex, cavernous sinus, clivus, medial aspect of the jugular foramen, or condylar regions are still difficult to fully expose using the operating microscope. Although approaches to this region through the middle cranial fossa have been previously described, these approaches afford only limited visualization. We have confirmed a transcranial infratemporal fossa combined microsurgical and endoscopic access to the petrous apex, clivus, medial aspect of the jugular foramen, and occipital condyle. We have presented the results of a micro-anatomical cadaver dissection study and its clinical application. METHODS: Ten latex-injected cadaveric specimens (20 twenty sides) underwent dissection with navigational guidance to achieve an extended anterior petrosal approach combined with a far vidian corridor approach (between the foramen rotundum and foramen ovale). We performed anatomical dissections to confirm the surgical anatomy and the feasibility and limitations of this approach. Anatomical dissections were performed in the skull base laboratory of Lariboisière Hospital and Duke University Medical Center. This approach was then applied to some clinical cases. RESULTS: The combination of the microscope and endoscope, aided by surgical navigation, was extremely effective and provided a wide view of the petrous rhomboid, the entire clivus, and the medial condylar regions. The extended extradural anterior petrosal approach provided a large corridor to petrous and clival lesions. Endoscopic assistance allows for wide and deep exposure of the middle to lower clivus, epipharyngeal space, and bilateral condylar regions. This approach successfully provided adequate surgical access for resection of tumors located in these regions. The depth of the medial aspect of the jugular foramen was 16.3 ± 1.2 mm deep from the geniculate ganglion. The emerging point of the inferior petrosal sinus in the jugular foramen was 16.5 ± 1.8 mm deep from the geniculate ganglion. The hypoglossal canal was 21.6 ± 2.2 mm deep from the geniculate ganglion. The foramen magnum was located 31.5 ± 2.4 mm deep from the gasserian ganglion. The inferior petrosal sinus was found to be a reliable landmark to identify the medial portion of the jugular bulb. The introduction of the endoscope through the middle fossa rhomboid enabled visualization of the medial aspect of the jugular bulb, which otherwise would be hampered by the internal auditory canal under the microscope. CONCLUSION: After microscopic exposure of the middle fossa rhomboid, neuronavigational endoscopic assistance facilitated visualization of the ventral cavernous region, petrous apex, retropharyngeal space, and middle and inferior clivus down to the medial aspect of the jugular bulb and condyle regions. Additional maxillary nerve-mandibular nerve vidian corridor visualization provides a lateral transsphenoidal approach to upper clivus lesions.

Rare Lesions of the Internal Auditory Canal.

BACKGROUND: Approximately 95% of tumors occurring within the internal auditory canal (IAC) are vestibular schwannomas. Many undergo stereotactic radiation without definitive tissue diagnosis. Rare IAC tumors are not all radiosensitive and are poorly described. METHODS: Between 1992 and 2015, 289 consecutive patients with IAC lesions operated on were reviewed retrospectively. RESULTS: Fifteen patients (5.2%) (16 operations) had unusual histologic findings, including nonvestibular schwannomas (2 facial schwannomas, 2 cochlear schwannomas, 2 intermedius schwannomas), 3 meningiomas, 3 cavernous hemangiomas, a mucosa-associated lymphoid tissue lymphoma, an arachnoid cyst, and a lipochoristoma. None of these rare tumors could be identified before surgery. Three operative approaches were used: the retrosigmoid approach, middle fossa subtemporal approach, or translabyrinthine approach. Few complications occurred, including facial nerve palsy, loss of hearing, and vestibular function. Five-year average follow-up revealed one patient with recurrence. CONCLUSIONS: Clinical examination and imaging alone were insufficient to correctly identify these tumors. Definitive pathologicdiagnosis should be strongly considered to help tailor treatment.

Isolated Deep Ear Canal Pain: Possible Role of Auricular Branch of Vagus Nerve-Case Illustrations with Cadaveric Correlation.

Glossopharyngeal, nervus intermedius, and vagus neuralgias can all present with ear pain. However, to our knowledge, there have been no reports of otalgia as the only symptom of vagus neuralgia. The seventh, ninth, and tenth cranial nerves have many interneural connections, and the exact anatomy and pathophysiology of these neuralgias are often not clear. Moreover, symptoms due to involvement of any of these nerves can be difficult to attribute solely to 1 of them. The overlapping sensory innervation of the external auditory canal can lead to misdiagnosis in patients suffering from otalgia. This report presents a case of pure otalgia due to vascular compression of the vagus nerve (VN) and considers the microanatomic differences between glossopharyngeal and nervus intermedius neuralgia via cadaveric dissections. We report 2 cases of external auditory canal pain that continued following microvascular treatment of trigeminal neuralgia. Intraoperatively and at secondary operation, the posterior inferior cerebellar artery was found to be adherent and to penetrate between the fibers of the VN. Following microvascular treatment of the VN, the pain resolved. CONCLUSION: This is the first report of vagus neuralgia presenting solely with ear pain. Surgeons should be aware that primary external auditory canal pain can be due to vagus neuralgia via its auricular branch and that such patients can be misdiagnosed with glossopharyngeal or nervus intermedius neuralgias.

Hepatic cystic echinococcosis with specific CT findings.

A hepatic central bisegmentectomy was performed on a 36-year-old Iranian man with suspected cystic echinococcosis. Hepatic computed tomography (CT) scan findings showed a large cystic lesion, which included many small round shaped cystic lesions. The diagnosis of hepatic cystic echinococcosis was confirmed during surgery. The aforementioned CT scan findings may be specific findings for cystic echinococcosis, in spite of a low appearance rate.