Middlebrooks, Erik H.

BACKGROUND AND OBJECTIVES: Surgical approaches to the ventral brainstem and petroclival regions are complex, and standard retrosigmoid and subtemporal approaches are often inadequate. Retrosigmoid suprameatal tubercle (RSMTA) and anterior subtemporal transpetrosal (ASTA) approaches may provide extended surgical exposure with less brain retraction. The objective of this study was to evaluate advantages and disadvantages of RSMTA vs ASTA, and illustrate the surgical corridors and 3-dimensional microsurgical anatomy of the related structures. METHODS: Four silicone-injected adult cadaver heads (8 sides) were dissected to evaluate the accessibility of lesions located at the petrous apex, ventral brainstem, and pontomedullary region using ASTA and RSTMA. RESULTS: Both ASTA and RSMTA provide access from the petrous apex to the ventral lower pons and pontomedullary junction. A greater extent of safely resected bone was found in ASTA vs RSMTA. ASTA provides a larger surgical view to the ventrolateral midpons, peritrigeminal region, superior neurovascular complex, pontomesencephalic junction, and posterior cavernous sinus. Meanwhile, through cranial nerve V mobilization, RSMTA provides a larger surgical view to the lower half part of the pons, ventrolateral part of the pontomedullary junction, and middle and lower neurovascular structures. CONCLUSION: The choice of surgical approach is determined by considering the area where the lesion originates, lesion size, the anatomic structures to which it extends, and evaluation of the area that can be surgically exposed. Our study highlights the differences between these approaches and important surgical anatomic considerations.

Transient global amnesia (TGA) is a neurological condition characterized by temporary memory loss and classically associated with a reversible unilateral punctate focus of restricted diffusion in the cornu ammonis 1 (CA1) region of the hippocampus. Historically, the lesions were considered to be transient in nature with no long-term imaging abnormality. However, more recent studies have challenged the concept that there are no long-term neurological sequelae. In line with this evidence, we explore the role of ultra-high-resolution imaging using 7 Tesla MRI to evaluate for long-term imaging abnormalities in a 63-year-old woman with a typical clinical course and acute TGA imaging findings. The 7 Tesla MRI revealed a residual lesion on susceptibility-weighted imaging (SWI) with evidence of gliosis and volume loss at the site of the acute lesion in CA1 eight months after the acute episode. This case challenges the traditional mantra of TGA as a fully reversible condition with no long-term imaging findings, suggesting the need for further research using ultra-high-field MRI to determine TGA's potential long-term imaging sequelae and any association with neurocognitive sequelae.

OBJECTIVE Pseudoaneurysms (PSAs) are complex vascular lesions. Flow diversion has been proposed as an alternative treatment to parent artery occlusion that preserves laminar flow. The authors of the present study investigated the safety and short-term (< 1 year) and long-term (≥ 1 year) aneurysm occlusion rates following the treatment of intracranial and extracranial PSAs using the Pipeline embolization device (PED). METHODS An electronic database search for full-text English-language articles in Ovid MEDLINE and Epub Ahead of Print, Ovid Embase, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus was conducted following the PRISMA guidelines. Studies of any design including at least 4 patients with intracranial or extracranial PSAs treated using a PED were included in this analysis. The primary outcome of interest was the rate of peri- and postprocedural complications. Secondarily, the authors analyzed the incidence of complete aneurysm occlusion. RESULTS A total of 90 patients with 96 PSAs across 9 studies were included. The mean age was 38.2 (SD 15.14) years, and 37.8% of the patients were women. The mean PSA size was 4.9 mm. Most PSAs were unruptured, and the most common etiology was trauma (n = 32, 35.5%), followed by spontaneous formation (n = 21, 23.3%) and iatrogenic injury (n = 19, 21.1%). Among the 51 (53.1%) intracranial and 45 (46.9%) extracranial PSAs were 19 (19.8%) dissecting PSAs. Sixty-six (77.6%) PSAs were in the internal carotid artery and 10 (11.8%) in the vertebral artery. Thirty-three (34.4%) PSAs were treated with ≥ 2 devices, and 8 (8.3%) underwent adjunctive coiling. The mean clinical and angiographic follow-up durations were 10.7 and 12.9 months, respectively. The short-term (< 1 year) and long-term (≥ 1 year) complete occlusion rates were 79% (95% CI 66%–88%, p = 0.82) and 84% (95% CI 70%–92%, p = 0.95), respectively. Complication rates were 8% for iatrogenic dissection (95% CI 3%–16%, p = 0.94), 10% for silent thromboembolism (95% CI 5%–21%, p = 0.77), and 12% for symptomatic thromboembolism (95% CI 6%–23%, p = 0.48). No treatment-related hemorrhage was observed. The overall mortality rate at the last follow-up was 14%. CONCLUSIONS The complete occlusion rate for PSAs treated with the PED was high and increased over time. Although postprocedural complications and mortality were not insignificant, flow diversion represents a reasonably safe option for managing these complex lesions.

The craniovertebral junction (CVJ) is a complex transition area between the skull and cervical spine. Pathologies such as chordoma, chondrosarcoma and aneurysmal bone cysts may be encountered in this anatomical area and may predispose individuals to joint instability. An adequate clinical and radiological assessment is mandatory to predict any postoperative instability and the need for fixation. There is no common consensus on the need for, timing and setting of craniovertebral fixation techniques after a craniovertebral oncological surgery. The aim of the present review is to summarize the anatomy, biomechanics and pathology of the craniovertebral junction and to describe the available surgical approaches to and considerations of joint instability after craniovertebral tumor resections. Although a one-size-fits-all approach cannot encompass the extremely challenging pathologies encountered in the CVJ area, including the possible mechanical instability that is a consequence of oncological resections, the optimal surgical strategy (anterior vs posterior vs posterolateral) tailored to the patient’s needs can be assessed preoperatively in many instances. Preserving the intrinsic and extrinsic ligaments, principally the transverse ligament, and the bony structures, namely the C1 anterior arch and occipital condyle, ensures spinal stability in most of the cases. Conversely, in situations that require the removal of those structures, or in cases where they are disrupted by the tumor, a thorough clinical and radiological assessment is needed to timely detect any instability and to plan a surgical stabilization procedure. We hope that this review will help shed light on the current evidence and pave the way for future studies on this topic.

Summary: The responsive neurostimulator continuously monitors the electrocorticogram. It delivers short bursts of high-frequency electrical stimulation when personalized patterns are detected. Intracranial EEG recording including electrocorticography is susceptible to artifacts, albeit at a lesser frequency compared with scalp recording. The authors describe a novel case of a patient with focal epilepsy, bitemporal responsive neurostimulation, and seizures without self-awareness manifest as focal impaired awareness seizures adversely affecting memory. At follow-up evaluation, the patient reported being clinically seizure-free although a single long episode was detected using the Patient Data Management System over the course of 3 years. Initial review identified a left-sided rhythmic discharge with a bilateral spatial field of involvement. In response to detection, the responsive neurostimulation delivered a series of five electrical stimulations. On further review, the patient recalled undergoing cervical radiofrequency ablation, which coincided with the appearance of the “electrographic seizure.” Extrinsic electrical artifact involving monomorphic nonevolving waveforms confirmed electrical artifact identified and treated by responsive neurostimulation as an epileptic seizure. On rare occasion, implanted electrical devices may lead to misdiagnosis and mistreatment of patients because of intracranial artifact.

There are many lesions that cause compression of nerves and vessels in the head and neck, and they can often be overlooked in the absence of adequate history or if not suspected by the radiologist. Many of these lesions require a high index of suspicion and optimal positioning for imaging. While a multimodality approach is critical in the evaluation of compressive lesions, an MRI utilizing high-resolution (heavily weighted) T2-weighted sequence is extremely useful as a starting point. In this review, we aim to discuss the radiological features of the common and uncommon compressive lesions of the head and neck which are broadly categorized into vascular, osseous, and miscellaneous etiologies.