Anatomic evaluation of the posterior temporal approach via the Heschl's gyrus to the thalamus, internal capsule, and atrium.

OBJECTIVE: Posterior temporal craniotomy allows for the exposure of the superior surface of the planum temporale. Heschl's gyrus is the most prominent structure of the planum temporale and can be an anatomical landmark to approach deep brain structures such as the internal capsule, lateral thalamus, and ventricular atrium. METHODS: Ten human cadavers' heads underwent a posterior bilateral temporal craniotomy and the microsurgical dissection of Heschl's gyrus was performed and variables were measured with a neuronavigation system and statistically analyzed. RESULTS: The mean distance between the keyhole and Heschl's gyrus was 61.7 ± 7.3 mm, the mean distance between the stephanion to Heschl's gyrus was 40.8 ± 6.0 mm, and the mean distance between the temporal lobe and Heschl's gyrus was 54.9 ± 6.9 mm. The length of Heschl's gyrus was 24 ± 7.5 mm, and the inclination angle in the axial plane was 20.0 ± 3.7° having the vertex as its deepest point as the base on the surface of the temporal plane. From Heschl's gyrus, the distance from the surface to the internal capsule was 29.1 ± 5.6 mm, the distance to the lateral thalamus was 34.8 ± 7.3 mm, and the distance to the ventricular atrium was 39.6 ± 7.2 mm. No statistical difference was found between the right and left sides. CONCLUSIONS: Through a posterior temporal craniotomy, the temporal planum is exposed by opening the Sylvian fissure, where Heschl's gyrus can be identified and used as a natural corridor to approach the internal capsule, the ventricular atrium, and the lateral thalamus.

Anatomic, qualitative, and quantitative evaluation of the variants of the infratentorial supracerebellar approach to the posteroinferior thalamus.

The posteroinferior region of the thalamus is formed by the pulvinar, and it is surgically accessed through the infratentorial supracerebellar approach, between the midline and the retromastoid region. This study aimed to compare the paramedian, lateral, extreme lateral, and contralateral paramedian corridors with the posteroinferior thalamus through a suboccipital craniotomy and an infratentorial supracerebellar access. Ten cadavers were studied, and the microsurgical dissections were accompanied by the measurement of the variables using a neuronavigation system. Statistical analysis was performed using analysis of variance (ANOVA). The distance between the access midpoint at the cranial surface and pulvinar varied between 53.3 and 53.9 mm, the contralateral access being an exception (59.9 mm). The vertical angle ranged from 20.6° in the contralateral access to 23.5° in the lateral access. There was a gradual increase in the horizontal angle between the paramedian (17.4°), lateral (31.3°), and extreme lateral (43.7°) accesses. But, this angle in the contralateral access was 14.6°, similar to that of the paramedian access. The exposed area of the thalamus was 125.1 mm2 in the paramedian access, 141.8 mm2 in the lateral access, and 165.9 mm2 in the extreme lateral access, which was similar to that of the contralateral access (164.9 mm2). The horizontal view angle increased with lateralization of the access, which facilitated microscopic visualization. With regard to the exposure of the microsurgical anatomy, the extreme lateral and contralateral accesses circumvent the neural and vascular obstacles at the midline, allowing a larger area of anatomical exposure.

Microsurgical Clipping of Ruptured Distal Posterior Inferior Cerebellar Artery Aneurysm: 3-Dimensional Operative Video.

The distal posterior inferior cerebellar artery (PICA) is a rare site of aneurysm formation. Only small case series and case reports regarding surgical treatment are found in the literature.The PICA is divided into 5 segments (anterior medullary, lateral medullary, tonsilomedullary, telovelotonsillary, and cortical), and the distal ones represent the most complex, due to anatomic variations. We present a case of a 69-yr-old female patient who has suffered from a sudden and intense occipital headache, associated with nausea and vomiting. CT scan showed intraventricular hemorrhage, and further investigation with MRI and MR Angiography revealed a small distal PICA aneurysm, at the superior part of the medial aspect of the left cerebellar tonsil. Digital angiography has demonstrated the aneurysm at the tonsilomedullary segment of the PICA. In this 3-dimensional video, the authors show the microsurgical clipping of a saccular distal PICA aneurysm in the close relation to a choroidal branch, performed by median suboccipital craniotomy. Step-by-step of the dissection, relevant surrounding anatomy and aneurysm clipping is demonstrated. The patient signed the Institutional Consent Form, which allows the use of his/her images and videos for any type of medical publications in conferences and/or scientific articles.

Microsurgery for Upper Basilar Tip Aneurysm With Intraoperative Rupture: 3-Dimensional Operative Video.

In the last years, a shift from the microsurgical treatment to an endovascular therapy in patients with basilar apex aneurysm has been settled, part of this phenomenon is related to the significant tendency of vital perforators to be involved in the aneurysm dissection and clipping, which can implicate unfavorable outcomes. Nevertheless, microsurgical treatment remains the treatment that can provide the superior rates of stable and durable aneurysm occlusion, which is most important to young patients.In this video, we present the case of a 45-yr-old female patient who complained of a sudden and severe headache and presented with progressive lethargy during the following 3 d.At admission, computed tomography did not show abnormal findings. However, cerebrospinal fluid analysis showed erythrocytes and corroborated the clinical suspicion of spontaneous subarachnoid hemorrhage. The patient signed the Institutional Consent Form, which allows the use of his/her images and videos for any type of medical publications in conferences and/or scientific articles.Angiography and magnetic resonance imaging revealed a saccular basilar apex aneurysm. It showed a wide neck as well as a lobulated dome with upward and slightly left projection. The aneurysm did not involve angiographically visible thalamoperforator arteries, which allowed the microsurgical treatment by the fronto-orbitozygomatic approach. However, during the interpeduncular cistern dissection, an intraoperative rupture of the aneurysm occurred. This video exemplifies the steps required to manage an intraoperative rupture of a basilar apex aneurysm.

Angular and metric analysis of the neural structures in the cerebellopontine angle.

INTRODUCTION: The cerebellopontine angle (CPA) is a subarachnoid space in the lateral aspect of the posterior fossa. In this study, we propose a complementary analysis of the CPA from the cerebellopontine fissure. METHODS: We studied 50 hemi-cerebelli in the laboratory of neuroanatomy and included a description of the CPA anatomy from the cerebellopontine fissure and its relationship with the flocculus and the 5th, 6th, 7th, and 8th cranial nerves (CN) origins. RESULTS: The average distance from the 5th CN to the mid-line (ML) was 19.2 mm, 6th CN to ML was 4.4 mm, 7-8 complex to ML was 15.8 mm, flocculus to ML was 20.5 mm, and flocculus to 5th CN was 11.5 mm, additionally, and the diameter of the flocculus was 9.0 mm. The angle between the vertex in the flocculus and the V CN and the medullary-pontine line was 64.8 degrees. DISCUSSION: The most common access to the CPA is through the retrosigmoid-suboccipital region and this approach can be done with the help of an endoscope. The anatomy of origins of neural structures tends to be preserved in cases of CPA lesions. CONCLUSION: Knowledge of the average distances between the neural structures in the cerebellar-pontine fissure and the angular relationships between these structures facilitates the use of surgical approaches such as microsurgery and endoscopy.

Treatment of Intradural Spinal Arteriovenous Fistula: Technical Case Report

Introduction Although rare, arteriovenous fistula (AVF) is the most common vascular malformation of the spine, and it is mainly located in the thoracic region. The fistula is identified by arteriography, which enables the treatment by embolization or guides the microsurgical therapy. Clinical Presentation We describe the case of a 61-year-old woman with neurogenic claudication evolving to paraparesis. A dorsal intradural AVF was identified by magnetic resonance imaging (MRI) and arteriography, and it was submitted to an embolization, but the procedure was unsuccessful. The patient was then referred for neurosurgery, and the AVF was obliterated using a microsurgical technique guided by multimodal intraoperative monitoring. We identified the AVF in the intraoperative moment and we then cut and coagulated the extradural portion of the nerve root. Discussion Arteriovenous fistulas occur in the dura mater of the nerve roots with the arterialization of the venous plexus. The treatment prevents the progression of the deficits. While performing diagnostic arteriography, attempts of embolization are possible. Conclusion Although the initial attempt of embolization at the moment of the diagnostic arteriography is achievable, it has failure rates of 50%, unlike the surgical treatment, which is definitive in all cases, as reported in this article.

Introdução Apesar de raras, as fístulas arteriovenosas (FAV) são as malformações vasculares mais comuns na coluna, localizadas essencialmente na região torácica. A fístula é identificada por arteriografia, a qual permite o tratamento da embolização ou guia a terapia microcirúrgica. Apresentação Clínica Descrevemos o caso de uma mulher de 61 anos com claudicação neurogênica evoluindo para paraparesia. Uma FAV intradural dorsal foi identificada por meio de ressonância magnética (RM) e arteriografia, e foi submetida a uma embolização, mas o procedimento não obteve sucesso. A paciente foi então encaminhada para tratamento neurocirúrgico, e a FAV foi eliminada por técnica microcirúrgica guiada por monitoração multimodal intraoperatória. Identificamos a FAV durante o período intraoperatório, e em seguida cortamos e coagulamos a porção extradural da raiz do nervo. Discussão As AVFs ocorrem na dura-máter das raízes neurais com a arterialização do plexo venoso. O tratamento evita o progresso de déficits. Durante a arteriografia diagnóstica, tentativas de embolização são possíveis. Conclusão Apesar de a tentativa inicial de embolização durante a arteriografia ser possível, ela tem probabilidades de 50% de sucesso, enquanto o tratamento cirúrgico é definitivo em todos os casos, como relatado neste artigo.