Fat graft-assisted internal auditory canal closure after retrosigmoid transmeatal resection of acoustic neuroma: Technique for prevention of cerebrospinal fluid leakage
The retrosigmoid transmeatal approach remains an important strategy in the surgical management of acoustic neuromas. Gross total resection of acoustic neuromas requires removal of tumor within the cerebellopontine angle as well as tumor involving the internal auditory canal (IAC). Drilling into the petrous bone of the IAC can expose petrous air cells, which can potentially result in a fistulous tract to the nasopharynx manifesting as cerebrospinal fluid (CSF) rhinorrhea. We describe our method of IAC closure using autologous fat graft and assessed the rates of postoperative CSF leakage. We performed a retrospective study of 24 consecutive patients who underwent retrosigmoid transmeatal resection of acoustic neuroma who underwent our method of fat graft-assisted IAC closure. We assessed rates of postoperative CSF leak (incisional leak, rhinorrhea, or otorrhea), pseudomeningocele formation, and occurrence of meningitis. Twenty-four patients (10 males, 14 females) with a mean age of 47 years (range 18-84) underwent fat graft-assisted IAC closure. No lumbar drains were used postoperatively. There were no instances of postoperative CSF leak (incisional leak, rhinorrhea, or otorrhea), pseudomeningocele formation, or occurrence of meningitis. There were no graft site complications. Our results demonstrate that autologous fat grafts provide a safe and effective method of IAC defect closure to prevent postoperative CSF leakage after acoustic tumor removal via a retrosigmoid transmeatal approach. The surgical technique and operative nuances are described.
Rapid evolution of in vivo-selected sequences and structures replacing 20% of a subviral RNA
The 356 nt noncoding satellite RNA C (satC) of Turnip crinkle virus (TCV) is composed of 5' sequences from a second TCV satRNA (satD) and 3' sequences derived from TCV. SHAPE structure mapping revealed that 76 nt in the poorly-characterized satD-derived region form an extended hairpin (H2). Pools of satC in which H2 was replaced with 76, 38, or 19 random nt were co-inoculated with TCV helper virus onto plants and satC fitness assessed using in vivo functional selection (SELEX). The most functional progeny satCs, including one as fit as wild-type, contained a 38-39 nt H2 region that adopted a hairpin structure and exhibited an increased ratio of dimeric to monomeric molecules. Some progeny of satC with H2 deleted featured a duplication of 38 nt, partially rebuilding the deletion. Therefore, H2 can be replaced by a 38-39 nt hairpin, sufficient for overall structural stability of the 5' end of satC.