Revealing the spatiotemporal brain dynamics of covert speech compared with overt speech: A simultaneous EEG-fMRI study.

Covert speech (CS) refers to speaking internally to oneself without producing any sound or movement. CS is involved in multiple cognitive functions and disorders. Reconstructing CS content by brain-computer interface (BCI) is also an emerging technique. However, it is still controversial whether CS is a truncated neural process of overt speech (OS) or involves independent patterns. Here, we performed a word-speaking experiment with simultaneous EEG-fMRI. It involved 32 participants, who generated words both overtly and covertly. By integrating spatial constraints from fMRI into EEG source localization, we precisely estimated the spatiotemporal dynamics of neural activity. During CS, EEG source activity was localized in three regions: the left precentral gyrus, the left supplementary motor area, and the left putamen. Although OS involved more brain regions with stronger activations, CS was characterized by an earlier event-locked activation in the left putamen (peak at 262 ms versus 1170 ms). The left putamen was also identified as the only hub node within the functional connectivity (FC) networks of both OS and CS, while showing weaker FC strength towards speech-related regions in the dominant hemisphere during CS. Path analysis revealed significant multivariate associations, indicating an indirect association between the earlier activation in the left putamen and CS, which was mediated by reduced FC towards speech-related regions. These findings revealed the specific spatiotemporal dynamics of CS, offering insights into CS mechanisms that are potentially relevant for future treatment of self-regulation deficits, speech disorders, and development of BCI speech applications.

Spontaneous Regression of a Large Vestibular Schwannoma: Is Nonoperative Management Reasonable?

Vestibular schwannomas (VSs) are the most common cerebellopontine tumors. The natural history of smaller-sized VSs (<30 mm) has been well-studied, leading to the recommendation of a "watch and wait" approach. However, large VSs (>30 mm) have not been extensively studied, mainly because of their rarity. As such, most patients are conventionally offered surgery which carries a significant risk of neurological morbidity. Here, we report a case of a giant VS (>40 mm) in a 30-year-old man who regressed spontaneously. He was lost to follow-up for 18 years and, upon re-presentation, the symptomatology drastically improved and repeat imaging demonstrated a marked reduction in tumor size. Referring to similar cases in other studies, we postulate that most large and giant VSs undergo a phase of growth and stasis, followed by regression due to shifts in the balance between tumorigenic and regressive factors. Taken together with emerging molecular data, further studies are required to better understand the history of large and giant VSs to shape more personalized treatment options. This potentially includes non-operative management as a tenable option.

Long-term outcome in extracranial-intracranial bypass surgery for severe steno-occlusive disease of intracranial internal carotid or middle cerebral artery.

OBJECTIVES: We report the long-term outcome and rates of recurrent cerebral ischemic events in our cohort of carefully selected patients after STA-MCA bypass for severe steno-occlusive disease of intracranial ICA or MCA with exhausted cerebral vasodilatory reserve. PATIENTS AND METHODS: In this retrospective study, we reviewed the hospital records for all patients who underwent direct superficial temporal artery-middle cerebral artery bypass surgery at our institution from January 2010 to August 2017. Patients were included in the study if they presented with transient ischemic attack or non-disabling stroke due to a severe steno-occlusive lesions of the intracranial internal carotid artery or middle cerebral artery with abnormal cerebral vasodilatory reserve on imaging. The overall event rate is defined as transient ischemic attack, acute ischemic stroke, peri-operative stroke or death. RESULTS: 69 patients were included in the study. The median age of cohort was 57 years (inter-quartile range 36-78). Median follow up period in our study was 73 months (range 2-90 months). The overall event rate post-treatment during the follow up period is 20.2%. In contrast, previous studies have showed that patients who underwent best medical therapy had a higher recurrent ischemic stroke rate over a 2-3-year period. CONCLUSION: This study suggests that carefully selected patients with severe steno-occlusive disease and significantly abnormal cerebral hemodynamic reserve who undergo extracranial-intracranial bypass surgery, may benefit from long-term prevention of symptomatic cerebral ischemic events.

Medical Support for Aircraft Disaster Search and Recovery Operations at Sea: the RSN Experience.

The maritime environment presents a unique set of challenges to search and recovery (SAR) operations. There is a paucity of information available to guide provision of medical support for SAR operations for aircraft disasters at sea. The Republic of Singapore Navy (RSN) took part in two such SAR operations in 2014 which showcased the value of a military organization in these operations. Key considerations in medical support for similar operations include the resultant casualty profile and challenges specific to the maritime environment, such as large distances of area of operations from land, variable sea states, and space limitations. Medical support planning can be approached using well-established disaster management life cycle phases of preparedness, mitigation, response, and recovery, which all are described in detail. This includes key areas of dedicated training and exercises, force protection, availability of air assets and chamber support, psychological care, and the forensic handling of human remains. Relevant lessons learned by RSN from the Air Asia QZ8501 search operation are also included in the description of these key areas. Teo KAC , Chong TFG , Liow MHL , Tang KC . Medical support for aircraft disaster search and recovery operations at sea: the RSN experience. Prehosp Disaster Med. 2016; 31(3):294-299.