Yun Mi Choi

Neural Ablation and Regeneration in Pain Practice

A nerve block is an effective tool for diagnostic and therapeutic methods. If a diagnostic nerve block is successful for pain relief and the subsequent therapeutic nerve block is effective for only a limited duration, the next step that should be considered is a nerve ablation or modulation. The nerve ablation causes iatrogenic neural degeneration aiming only for sensory or sympathetic denervation without motor deficits. Nerve ablation produces the interruption of axonal continuity, degeneration of nerve fibers distal to the lesion (Wallerian degeneration), and the eventual death of axotomized neurons. The nerve ablation methods currently available for resection/removal of innervation are performed by either chemical or thermal ablation. Meanwhile, the nerve modulation method for interruption of innervation is performed using an electromagnetic field of pulsed radiofrequency. According to Sunderlands classification, it is first and foremost suggested that current neural ablations produce third degree peripheral nerve injury (PNI) to the myelin, axon, and endoneurium without any disruption of the fascicular arrangement, perineurium, and epineurium. The merit of Sunderlands third degree PNI is to produce a reversible injury. However, its shortcoming is the recurrence of pain and the necessity of repeated ablative procedures. The molecular mechanisms related to axonal regeneration after injury include cross-talk between axons and glial cells, neurotrophic factors, extracellular matrix molecules, and their receptors. It is essential to establish a safe, long-standing denervation method without any complications in future practices based on the mechanisms of nerve degeneration as well as following regeneration.

Etifoxine for Pain Patients with Anxiety

Etifoxine (etafenoxine, Stresam®) is a non-benzodiazepine anxiolytic with an anticonvulsant effect. It was developed in the 1960s for anxiety disorders and is currently being studied for its ability to promote peripheral nerve healing and to treat chemotherapy-induced pain. In addition to being mediated by GABAAα2 receptors like benzodiazepines, etifoxine appears to produce anxiolytic effects directly by binding to β2 or β3 subunits of the GABAA receptor complex. It also modulates GABAA receptors indirectly via stimulation of neurosteroid production after etifoxine binds to the 18 kDa translocator protein (TSPO) of the outer mitochondrial membrane in the central and peripheral nervous systems, previously known as the peripheral benzodiazepine receptor (PBR). Therefore, the effects of etifoxine are not completely reversed by the benzodiazepine antagonist flumazenil. Etifoxine is used for various emotional and bodily reactions followed by anxiety. It is contraindicated in situations such as shock, severely impaired liver or kidney function, and severe respiratory failure. The average dosage is 150 mg per day for no more than 12 weeks. The most common adverse effect is drowsiness at the initial stage. It does not usually cause any withdrawal syndromes. In conclusion, etifoxine shows less adverse effects of anterograde amnesia, sedation, impaired psychomotor performance, and withdrawal syndromes than those of benzodiazepines. It potentiates GABAA receptor-function by a direct allosteric effect and by an indirect mechanism involving the activation of TSPO. It seems promising that non-benzodiazepine anxiolytics including etifoxine will replenish shortcomings of benzodiazepines and selective serotonin reuptake inhibitors according to animated studies related to TSPO.

Left ventricular outflow tract obstruction due to a left ventricular myxoma that was misidentified as an accessory mitral valve tissue

We report obstruction of the left ventricle outflow tract (LVOT) caused by cardiac myxoma that was misidentified as an accessory mitral valve tissue preoperatively. A 65-year-old woman presented with chest discomfort that persisted for 7 days. Transthoracic echocardiography (TTE) revealed a mobile, low-echogenic, balloon-shaped mass attached to the anterior mitral valve leaflet and papillary muscle, which was suspected to be an accessory mitral valve tissue. Because the mass caused LVOT obstruction and it could result in hemodynamic instability, emergency operation was performed. Intraoperative transesophageal echocardiography (TEE) was performed, and the mass had irregular margins and was pedunculated, with a stalk originating from the left ventricle (LV) wall and extending to the lateral chordae of the mitral valve. The surgeon excised the mass filled with the myxomatous mass, which was yellowish and gelatinous and had a stiff stalk, and histopathologic diagnosis confirmed a myxoma. Although mitral valve or LV myxomas are rare, TEE is a useful tool for distinguishing a myxoma from other intracardiac masses, such as vegetation or an accessory mitral valve tissue.