[Intraoperative Monitoring During Microvascular Decompression].

During microvascular decompression(MVD)for hemifacial spasm(HFS), trigeminal neuralgia(TN), and glossopharyngeal neuralgia(GPN), brainstem auditory-evoked potential monitoring is widely used to preserve hearing function. In MVD for HFS, abnormal muscle response monitoring is useful for identifying the offending vessels compressing the facial nerve and confirming the completion of decompression intraoperatively. The amplitude of facial motor-evoked potential by transcranial electrical stimulation in the orbicularis oculi muscle is reported to decrease after completing MVD. The Z-L response(ZLR)probably confirms the true offending vessels by stimulating the culprit vessels; then, the ZLR could disappear after decompressing the offending vessels away from the compression sites. Spontaneous electromyographic activities obtained from the mentalis muscles by injection of saline into the facial nerve reportedly decreased after MVD compared with those before MVD. In MVD for the GPN, glossopharyngeal motor-evoked potential by transcranial electrical stimulation is used to preserve swallowing function and not to assess the completion of MVD. Because MVD for both the TN and GPN can result in normalization of the hyperactivity of the sensory nerve, it may be difficult to develop any monitoring to confirm the completion of MVD during surgery.

Indications for a brain biopsy in neurological diseases of unknown etiology: The role of magnetic resonance imaging findings and liquid biopsy in yielding definitive pathological diagnoses.

Brain biopsies are often considered for patients who cannot be diagnosed with various laboratory test results. However, physicians tend to be hesitant regarding their application in possibly non-neoplastic brain diseases, due to the invasiveness and risks. The aim was to determine the indications for brain biopsies in cases of neurological diseases of unknown etiology. We retrospectively evaluated diagnostic accuracy, laboratory findings (including a liquid biopsy for malignant lymphoma), magnetic resonance imaging (MRI) characteristics and the post-treatment outcomes of patients undergoing brain biopsies for neurological diseases of unknown etiology. The data of patients who had undergone a brain biopsy during their admission to Niigata University Hospital, between 2011 and 2024, were reviewed. Moreover, the laboratory data and MRI findings between patients with definitive and nonspecific biopsy diagnoses were compared. Twenty-six patients underwent a brain biopsy, and a definitive diagnosis was obtained in 14 patients (53.8%). Even in cases where a nonspecific diagnosis was made, biopsy findings helped rule out malignancy and guide clinical diagnosis and treatment decisions. The liquid biopsy for malignant lymphoma was performed in eight patients, with one yielding a positive result, consistent with primary central nervous system lymphoma. The sensitivity and specificity of liquid biopsy were 0.5 and 1, respectively. Diffusely contrasted cortical lesions and the presence of mass effects on MRI, were significantly associated with a definitive diagnosis, compared to a nonspecific diagnosis. In conclusion, brain MRI and liquid biopsies can assist in determining the appropriate indications for brain biopsies in neurological diseases of unknown etiology.