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## Antonius Balthazar Raymundus Hirsch and the peregrination of “gasserian ganglion”

### Historical vignette

The anatomical description of the fifth cranial nerve ganglion lacked detail before the work of Antonius Balthazar Raymundus Hirsch (1744–1778). Hirsch used new dissection techniques that resulted in the most meticulous report of the trigeminal ganglion (the gasserian ganglion) to have been reported. In 1765, the 21-year-old published these findings in a thesis, Paris Quinti Nervorum Encephali Disquisitio Anatomica In Quantum Ad Ganglion Sibi Proprium, Semilunare, Et Ad Originem Nervi Intercostalis Pertinet [An anatomical inquiry of the fifth pair of the nerves of the brain, so far as it relates to the ganglion unto itself, the semilunar, and to the source of the intercostal nerve].

Hirsch wrote his thesis as a paean to his ailing teacher, Johann Lorenz Gasser, but Gasser died before Hirsch was able to defend his thesis. Thereafter, Hirsch applied to teach anatomy at his alma mater, the University of Vienna, but the university did not consider his application, deeming him too young for the position. Oddly, Hirsch died at the young age of 35. For the present paper, the library at the University of Vienna (Universität Wien), Austria, was contacted, and Anton Hirsch's thesis was digitized and subsequently translated from Latin into English. The authors here attempt to place the recognition of the fifth cranial nerve ganglion within a historical perspective and trace the trajectory of its anatomical descriptions.

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## Perioperative complications in patients undergoing open transforaminal lumbar interbody fusion as a revision surgery

### Object

Transforaminal lumbar interbody fusion (TLIF) has been increasingly used to treat degenerative spine disease, including that in patients in whom earlier decompressive procedures have failed. Reexploration in these cases is always challenging and is thought to pose a higher risk of complications. To the best of the authors' knowledge, there are no current studies specifically analyzing the effects of previous lumbar decompressive surgeries on the complication rates of open TLIF.

### Methods

The authors performed a retrospective study of surgeries performed by a single surgeon. A total of 187 consecutive patients, in whom the senior author (A.N.) had performed open TLIF between January 2007 and January 2011, met the inclusion criteria. The patients were divided into two groups (primary and revision TLIF) for the comparison of perioperative complications.

### Results

Overall, the average age of the patients was 49.7 years (range 18–80 years). Of the 187 patients, 73 patients had no history of lumbar surgery and 114 were undergoing revision surgery. Fifty-four patients (28.9%) had a documented complication intraoperatively or postoperatively. There was no difference in the rate on perioperative complications between the two groups (overall, medical, wound related, inadvertent dural tears [DTs], or neural injury). Patients who had undergone more than one previous lumbar surgery were, however, more likely to have suffered from DTs (p = 0.054) and neural injuries (p = 0.007) compared with the rest.

### Conclusions

In the hands of an experienced surgeon, revision open TLIF does not necessarily increase the risk of perioperative complications compared with primary TLIF. Two or more previous lumbar decompressive procedures, however, increase the risk of inadvertent DTs and neural injury.

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## Do cystic vestibular schwannomas have worse surgical outcomes? Systematic analysis of the literature

### Object

The goal of this study was to perform a systematic quantitative comparison of the surgical outcomes between cystic vestibular schwannomas (CVSs) and solid vestibular schwannomas (SVSs).

### Methods

A review of English-language literature published between 1990 and 2011 was performed using various search engines including PubMed, Google Scholar, and the Cochrane database. Only studies that reported surgical results of CVSs in comparison with SVSs were included in the analysis. The primary end point of this study was surgical outcomes, defined by the following: 1) facial nerve outcomes at latest follow-up; 2) mortality rates; or 3) non–facial nerve complication index. Secondary end points included extent of resection and brainstem adherence.

### Results

Nine studies comprising 428 CVSs and 1287 SVSs were included in the study. The mean age of patients undergoing surgery was 48.3 ± 6.75 and 47.1 ± 9 years for CVSs and SVSs, respectively (p = 0.8). The mean tumor diameter for CVSs was 3.9 ± 0.84 cm and that for SVSs was 3.7 ± 1.2 cm (p = 0.7). There was no significant difference in the extent of resection among CVSs and SVSs (81.2% vs 80.7%, p = 0.87) Facial nerve outcomes were significantly better in the cohort of patients with SVSs than in those with CVSs (52.1% vs 39%, p = 0.0001). The perioperative mortality rates for CVSs and SVSs were not significantly different (3% and 3.8%, respectively; p = 0.6). No significant difference was noted between the cumulative non–facial nerve complication rate (including mortality) among patients with CVSs and SVSs (24.5% and 25.6%, respectively; p = 0.75)

### Conclusions

Facial nerve outcomes are worse in patients undergoing resection for CVSs than in patients undergoing resection for SVSs. There were no significant differences in the extent of resection or postoperative morbidity and mortality rates between the cohorts of patients with vestibular schwannomas.

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## The impact of comorbidities, regional trends, and hospital factors on discharge dispositions and hospital costs after acoustic neuroma microsurgery: a United States nationwide inpatient data sample study (2005–2009)

### Object

Hospitalization cost and patient outcome after acoustic neuroma surgery depend on several factors. There is a paucity of data regarding the relationship between demographic features such as age, sex, race, insurance status, and patient outcome. Apart from demographic factors, there are several hospital-related factors and regional issues that can affect outcomes and hospital costs. To the authors' knowledge, no study has investigated the issue of regional disparity across the country in terms of cost of hospitalization and discharge disposition.

### Methods

The authors analyzed the Nationwide Inpatient Sample (NIS) database over the years 2005–2009. Several variables were analyzed from the database, including patient demographics, comorbidities, and surgical complications. Hospital variables, such as bedsize, rural/urban location, teaching status, federal or private ownership, and the region, were also examined. Patient outcome and increased hospitalization costs were the dependent variables studied.

### Results

A total of 2589 admissions from 242 hospitals were analyzed from the NIS data over the years 2005–2009. The mean age was 48.99 ± 13.861 years (± SD), and 304 (11.7%) of the patients were older than 65 years. The cumulative cost incurred by the hospitals from 2005 to 2009 was $948.77 million. The mean expenditure per admission was$76,365.09 ± $58,039.93. The mean total charges per admission rose from$59,633.00 in 2005 to \$97,370.00 in 2009. The factors that predicted most significantly with other than routine (OTR) disposition outcome were age older than 65 years (OR 2.22, 95% CI 1.411–3.518; p < 0.001), aspiration pneumonia (OR 16.085, 95% CI 4.974–52.016; p < 0.001), and meningitis (OR 11.299, 95% CI 3.126–40.840; p < 0.001). When compared with patients with Medicare and Medicaid, patients with private insurance had a protective effect against OTR disposition outcome. Higher comorbidities predicted independently for OTR disposition outcome (OR 1.409, 95% CI 1.072–1.852; p = 0.014). The West region predicted negatively for OTR disposition outcome. Large hospitals were independently associated with higher hospital charges (OR 4.269, 95% CI 3.106–5.867; p < 0.001). The West region had significantly higher (p < 0.001) mean hospital charges than the other regions. Patient factors such as meningitis and aspiration pneumonia were strong independent predictors of increased hospital charges (p < 0.001). Higher comorbidities (OR 1.297, 95% CI 1.036–1.624; p = 0.023) and presence of neurofibromatosis Type 2 (OR 2.341, 95% CI 1.479–3.707; p < 0.001) were associated with higher hospital charges.

### Conclusions

The authors' study shows that several factors can affect patient outcome and hospital charges for patients who have undergone acoustic neuroma surgery. Factors such as younger age, higher ZIP code income, less comorbidity, private insurance, elective surgery, and the West region predicted for better disposition outcome. However, the West region, higher comorbidities, and weekend admissions were associated with higher hospitalization costs.

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## An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios.

Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

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## Humphrey Ridley (1653–1708): 17th century evolution in neuroanatomy and selective cerebrovascular injections for cadaver dissection

Humphrey Ridley, M.D. (1653–1708), is a relatively unknown historical figure, belonging to the postmedieval era of neuroanatomical discovery. He was born in the market town of Mansfield, 14 miles from the county of Nottinghamshire, England. After studying at Merton College, Oxford, he pursued medicine at Leiden University in the Netherlands. In 1688, he was incorporated as an M.D. at Cambridge. Ridley authored the first original treatise in English language on neuroanatomy, The Anatomy of the Brain Containing its Mechanisms and Physiology: Together with Some New Discoveries and Corrections of Ancient and Modern Authors upon that Subject.

Ridley described the venous anatomy of the eponymous circular sinus in connection with the parasellar compartment. His methods were novel, unique, and effective. To appreciate the venous anatomy, he preferred to perform his anatomical dissections on recently executed criminals who had been hanged. These cadavers had considerable venous engorgement, which made the skull base venous anatomy clearer. To enhance the appearance of the cerebral vasculature further, he used tinged wax and quicksilver in the injections. He set up experimental models to answer questions definitively, in proving that the arachnoid mater is a separate meningeal layer. The first description of the subarachnoid cisterns, blood-brain barrier, and the fifth cranial nerve ganglion with its branches are also attributed to Ridley.

This historical vignette revisits Ridley's life and academic work that influenced neuroscience and neurosurgical understanding in its infancy. It is unfortunate that most of his novel contributions have gone unnoticed and uncited. The authors hope that this article will inform the neurosurgical community of Ridley's contributions to the field of neurosurgery.

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## Is posttraumatic cerebrospinal fluid fistula a predictor of posttraumatic meningitis? A US Nationwide Inpatient Sample database study

### Object

Various factors have been reported in literature to be associated with the development of posttraumatic meningitis. There is a paucity of data regarding skull fractures and facial fractures leading to CSF leaks and their association with the development of meningitis. The primary objective of this study was to analyze the US Nationwide Inpatient Sample (NIS) database to elucidate the factors associated with the development of posttraumatic meningitis. A secondary goal was to analyze the overall hospitalization cost related to posttraumatic meningitis and factors associated with that cost.

### Methods

The NIS database was analyzed to identify patients admitted to hospitals with a diagnosis of head injury from 2005 through 2009. This data set was analyzed to assess the relationship of various clinical parameters that may affect the development of posttraumatic meningitis using binary logistic regression models. Additionally, the overall hospitalization cost for the head injury patients who did not undergo any neurosurgical intervention was further categorized into quartile groups, and a regression model was created to analyze various factors responsible for escalating the overall cost of the hospital stay.

### Results

A total of 382,267 inpatient admissions for head injury were analyzed for the 2005–2009 period. Meningitis was reported in 0.2% of these cases (708 cases). Closed skull base fractures, open skull base fractures, cranial vault fractures, and maxillofacial fractures were reported in 20,524 (5.4%), 1089 (0.3%), 5064 (1.3%), and 88,649 (23.2%) patients, respectively. Among these patients with fractures, meningitis was noted in 0.17%, 0.18%, 0.05%, and 0.10% admissions, respectively. Cerebrospinal fluid rhinorrhea was reported in 453 head injury patients (0.1%) and CSF otorrhea in 582 (0.2%). Of the patients reported to have CSF rhinorrhea, 35 (7.7%) developed meningitis, whereas in the cohort with CSF otorrhea, 15 patients (2.6%) developed meningitis. Cerebrospinal fluid rhinorrhea (p < 0.001, OR 22.8, 95% CI 15.6–33.3), CSF otorrhea (p < 0.001, OR 9.2, 95% CI 5.2–16.09), and major neurosurgical procedures (p < 0.001, OR 5.6, 95% CI 4.8–6.5) were independent predictors of meningitis. Further, CSF rhinorrhea (p < 0.001, OR 2.0, 95% CI 1.6–2.7), CSF otorrhea (p < 0.001, OR 2.3, 95% CI 1.9–2.7), and posttraumatic meningitis (p < 0.001, OR 3.1, 95% CI 2.5–3.8) were independent factors responsible for escalating the cost of head injury in cases not requiring any major neurosurgical intervention.

### Conclusions

Cerebrospinal fluid rhinorrhea and CSF otorrhea are independent predictors of posttraumatic meningitis. Furthermore, meningitis and CSF fistulas may independently lead to significantly increased cost of hospitalization in head injury patients not undergoing any major neurosurgical intervention.