Introduction: Among the primary lesions occupying the spinal space, only 1% corresponds to the epidural arachnoid cyst (EAC). This condition is usually asymptomatic, and identified accidentally in imaging tests. In symptomatic cases, total surgical resection is recommended. Objective: To describe a case of EAC refractory to clinical treatment. Methods: A 45-year-old woman had lumbar pain for six years and increased pain in the last months, with irradiation to the left lower limb (corresponding to L1). No other alterations found in the physical examination. Magnetic resonance imaging (MRI) of the spine revealed an intravertebral cystic lesion at T12-L1 level, in the left posterolateral position, causing enlargement of the foramen, and suggesting an epidural arachnoid cyst. Results: Due to failure of the initial clinical treatment, the patient underwent left T12-L1 hemilaminectomy, resection of the cyst and correction of dural failure. The patient progressed with effective pain control and MRI confirmed absence of residual lesion. Conclusion: EAC is more common in men (4:1) and may be congenital or acquired. The most common topography is thoracic (65%). Its clinical presentation is low back pain, lower limb pain and paresthesia. MRI is the method of choice for diagnosis and surgical intervention is restricted to cases that are symptomatic or refractory to clinical treatment, and the prognosis tends to be excellent. We conclude that, in addition to being a rare and commonly asymptomatic condition, an adequate therapeutic approach is essential for complete cure, avoiding intense pain and manifestations that bring about a drastic reduction of functional capacity. Level of evidence: IV. Type of study: Case series.

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Posterior fossa epidermoid cysts are slow growing lesions that can present with involvement of multiple neurovascular structures. [1][2][3][4][5][6] We present the case of a 49-year-old woman with a long-term history of headache, imbalance, nausea and vomiting, and hearing loss. Gait disturbance was also identified on physical examination. Preoperative MRI demonstrated a lesion highly suggestive of a giant posterior fossa epidermoid cyst with significant compression of the brainstem and bilateral extension. Because of the important mass effect and worsening of symptoms, microsurgical resection was indicated. A presigmoid (posterior petrosal) approach combined with a retrosigmoid route was used, and neurophysiological monitoring was essential during the procedure. The patient was placed in a true lateral position, and initially, the mastoidectomy was performed, followed by the craniotomy encompassing both middle and posterior cranial fossae. Dural incisions posterior and anterior to sigmoid sinus were performed. An incision at the base of the middle fossa dura was connected with the presigmoid one by ligation of the superior petrosal sinus. Then, the tentorium was all the way cut toward incisura. Multiple working corridors were provided, and the lesion was completely resected. A third ventriculostomy was also performed considering preoperative hydrocephalus. Postoperative imaging demonstrated complete lesion removal. The patient presented improvement of symptoms and evolved with a slight left facial palsy contralateral to the side of the approach, progressively recovering with physical therapy. Laboratory training is essential to get familiarized with the neuroanatomic nuances of this approach. Informed consent was obtained from the patient for the procedure and publication of her images in this operative video.

Ischemia of the optic nerve (ON) is an important cause of visual field deficit provoked by tuberculum sellae (TS) meningiomas. Indocyanine green (ICG) videoangiography could provide prognostic information. Moreover, it allows new insight into the pathophysiology of visual disturbance. The authors present the case of a 48-year-old woman with visual field impairment. Magnetic resonance imaging (MRI) depicted a lesion highly suggestive of a TS meningioma. Following microsurgical resection, ICG videoangiography demonstrated improvement of right ON pial blood supply. In this case, there was one lesion causing visual impairment through both direct compression over the left ON and ischemia to the right nerve. The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21155

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