Management of traumatic subarachnoid hemorrhage by the trauma service: is repeat CT scanning and routine neurosurgical consultation necessary?

Subarachnoid hemorrhage (SAH) results frequently from traumatic brain injury (TBI). The standard management for these patients includes brief admission by the acute care surgery (trauma) service with neurological checks, neurosurgical consultation and repeat head CT within 24 hours to identify any progression or resolution. Recent studies have questioned the need for repeat CT imaging and specialty consultation in mild TBI. We reviewed patients with mild TBI specifically with isolated SAH to determine progression of the pathology and need for neurosurgical involvement. All patients with SAH secondary to mild TBI (Glasgow Coma Score (GCS) of 13-15) who presented over a 5-year period (January 2010 to December 2014) to a level I trauma center were identified from the trauma registry. Demographic data, initial CT findings, neurosurgical consultation, follow-up CT findings, Injury Severity Score (ISS), admission GCS and length of stay (LOS) were all obtained from the patient's charts. Patients with other traumatic brain lesions on the initial CT were excluded. There were 299 patients (male, 48.5%), mean age 60.9 and mean ISS 8. Average time between the first and second CT was 11.3 hours. In all, 267 (89.2%) patients had either no change or an improvement/resolution on follow-up CT scan. Only 26 patients (8.7%) had either worsening or new findings on CT. Eight patients did not have a second scan completed (2.6%). All patients had neurosurgical consultation. Patients with mild TBI with isolated SAH generally have low morbidity, short LOS and negligible mortality. Less than 10% of this population had worsening of their head injury on repeat CT scanning. Given the low acuity of these patients with SAH and tendency towards resolution without intervention, acute care surgeons can manage this specific group of patients with TBI without routine neurosurgical consultation. Repeat CT scanning continues to have utility as it may identify new lesions, deterioration or need for further management.

Interrogating the function of metazoan histones using engineered gene clusters.

Histones and their posttranslational modifications influence the regulation of many DNA-dependent processes. Although an essential role for histone-modifying enzymes in these processes is well established, defining the specific contribution of individual histone residues remains a challenge because many histone-modifying enzymes have nonhistone targets. This challenge is exacerbated by the paucity of suitable approaches to genetically engineer histone genes in metazoans. Here, we describe a platform in Drosophila for generating and analyzing any desired histone genotype, and we use it to test the in vivo function of three histone residues. We demonstrate that H4K20 is neither essential for DNA replication nor for completion of development, unlike inferences drawn from analyses of H4K20 methyltransferases. We also show that H3K36 is required for viability and H3K27 is essential for maintenance of cellular identity but not for gene activation. These findings highlight the power of engineering histones to interrogate genome structure and function in animals.