Symptomatic and Radiographic Improvement Following Surgery for Posterior Fossa Arachnoid Cysts: Meta-Analysis and Literature Review.

OBJECTIVE: Arachnoid cysts are benign, intradural collections of cerebrospinal fluid that are often asymptomatic but, in rare instances, will grow and may cause symptoms. When these are in the posterior fossa, the symptomatology greatly ranges, and the indications for surgery are not well defined. The objective of this study is to examine radiographic and symptomatic outcomes following surgery for posterior fossa arachnoid cysts (PFAC). METHODS: A literature review was performed utilizing PubMed for all studies involving ≥ 5 patients with PFACs who underwent surgery. A single-arm meta-analysis was performed to assess the postoperative radiographic improvement. Given the heterogeneous variety of presenting symptoms, these were not conducive to meta-analyses but the outcomes are reported in detail. RESULTS: Nine publications with 67 patients met inclusion criteria. Excision/fenestration was the most common operation (n=60). Less common included CP shunts (n=2), concurrent excision/fenestration and ETV (n=4), and one patient who underwent concurrent VP/CP shunts. This literature review revealed improvement of headache in 90% of patients; 88% with cerebellar symptoms; 92% with nausea/emesis; 78% with hearing loss; 60% with tinnitus; and 91% with vision deficits. Meta-analysis of seven studies reporting postoperative radiographic size demonstrated that 75% of people experienced decreased PFAC size (Effect Size: 0.75, 95% CI: 0.50-0.94). CONCLUSIONS: Although there is a high rate of radiographic improvement for PFAC surgery, there is a wide variety of presenting symptoms with differing postoperative improvement rates. This study reinforces the importance of preoperative counseling regarding symptomatic outcomes for PFAC surgery, with supporting statistical analysis but limited by the sample sizes available.

No change in network connectivity measurements between separate rsfMRI acquisition times.

The role of resting state functional MRI (rsfMRI) is increasing in the field of epilepsy surgery because it is possible to interpolate network connectivity patterns across the brain with a high degree of spatial resolution. Prior studies have shown that by rsfMRI with scalp electroencephalography (EEG), an epileptogenic network can be modeled and visualized with characteristic patterns of connectivity that are relevant to both seizure-related and neuropsychological outcomes after surgery. The aim of this study is to show that a 5-min acquisition time provides reproducible results related to the relevant connectivity metrics when compared to a separately acquired 5-min scan. Fourteen separate rsfMRI sessions from ten different patients were used for comparison, comprised of patients with temporal lobe epilepsy both pre- and post-operation. Results showed that there was no significant difference in any of the connectivity metrics when comparing both 5-min scans to each other. These data support the continued use of a 5-min scan for epileptogenic network modeling in future studies because the inter-scan variability is sufficiently low as not to alter the output metrics characterizing the network connectivity.

Incidental Metaplastic Primary Pulmonary Meningioma.

Primary pulmonary meningioma is a rare benign tumor usually presenting as a solitary pulmonary nodule or mass. It can be easily misinterpreted as a primary lung tumor or metastases on imaging studies. We present a 54-year-old woman with an incidentally discovered solitary lung nodule, which was diagnosed as metaplastic primary pulmonary meningioma following resection. Metaplastic meningioma is a rare WHO grade 1 meningioma subtype with focal or global mesenchymal differentiation. To the authors' knowledge, primary pulmonary meningioma with mesenchymal differentiation has not been described previously in the English literature.