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## Bengt Liliequist: life and accomplishments of a true renaissance man

In the 1970s, the membrane of Liliequist became the accepted name for a small band of arachnoid membrane separating the interpeduncular and chiasmatic cisterns, making it one of the most recent of the universally accepted medical eponyms. The story of its discovery, however, cannot be told without a thorough understanding of the man responsible and his contribution to the growth of a specialty. Bengt Liliequist lived during what many would consider the Golden Age of neuroradiology. With his colleagues at the Serafimer Hospital in Stockholm, he helped set the standard for appropriate imaging of the CNS and contributed to more accurate localization of intracerebral as well as spinal lesions. The pneumoencephalographic discovery of the membrane that was to bear his name serves merely as a starting point for a career that spanned five decades and included the defense of two separate doctoral theses, the last of which occurred after his 80th birthday. Although the recognition of neuroradiology as a subspecialty did not occur in his home country of Sweden until after his retirement, and technological progress saw the obsolescence of the procedure that he had mastered, Dr. Liliequist's accomplishments and his contributions to the current understanding of neuroanatomy merit our continued praise.

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## A comparison of lumboperitoneal and ventriculoperitoneal shunting for idiopathic intracranial hypertension: an analysis of economic impact and complications using the Nationwide Inpatient Sample

### Object

Complications following lumboperitoneal (LP) shunting have been reported in 18% to 85% of cases. The need for multiple revision surgeries, development of iatrogenic Chiari malformation, and frequent wound complications have prompted many to abandon this procedure altogether for the treatment of idiopathic benign intracranial hypertension (pseudotumor cerebri), in favor of ventriculoperitoneal (VP) shunting. A direct comparison of the complication rates and health care charges between first-choice LP versus VP shunting is presented.

### Methods

The Nationwide Inpatient Sample database was queried for all patients with the diagnosis of benign intracranial hypertension (International Classification of Diseases, Ninth Revision, code 348.2) from 2005 to 2009. These data were stratified by operative intervention, with demographic and hospitalization charge data generated for each.

### Results

A weighted sample of 4480 patients was identified as having the diagnosis of idiopathic intracranial hypertension (IIH), with 2505 undergoing first-time VP shunt placement and 1754 undergoing initial LP shunt placement. Revision surgery occurred in 3.9% of admissions (n = 98) for VP shunts and in 7.0% of admissions (n = 123) for LP shunts (p < 0.0001). Ventriculoperitoneal shunts were placed at teaching institutions in 83.8% of cases, compared with only 77.3% of first-time LP shunts (p < 0.0001). Mean hospital length of stay (LOS) significantly differed between primary VP (3 days) and primary LP shunt procedures (4 days, p < 0.0001). The summed charges for the revisions of 92 VP shunts ($3,453,956) and those of the 6 VP shunt removals ($272,484) totaled $3,726,352 over 5 years for the study population. The summed charges for revision of 70 LP shunts ($2,229,430) and those of the 53 LP shunt removals ($3,125,569) totaled$5,408,679 over 5 years for the study population.

### Conclusions

The presented results appear to call into question the selection of LP shunt placement as primary treatment for IIH, as this procedure is associated with a significantly greater likelihood of need for shunt revision, increased LOS, and greater overall charges to the health care system.

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## From Pergamon to Army Base Hospital No. 5: the history and significance of the galea aponeurotica in the evolution of neurosurgery

### Historical vignette

The authors trace the etymology and historical significance of galea or epicranial aponeurosis. In ancient Greece, galea referred to a helmet worn by soldiers, typically made of animal hide or leather. Throughout antiquity, physicians referred to all soft tissue between the skin and the skull as panniculus, a standard established by Galen of Pergamon. A manual of surgery in the Middle Ages referred to the entire scalp as a “great panicle that is called pericranium.” During the early Renaissance, Leonardo da Vinci famously and stylistically analogized the dissection of the cranium with the peeling of an onion. Not until 1724 would the tendinous sheath connecting the frontalis and occipitalis muscles be defined as “Galea tendinosa cranii.” By 1741, the convention of referring to the galea as an aponeurosis was well established.

Harvey Cushing's wartime experiences at Army Base Hospital No. 5 reinforced the surgical significance of the galea. Operative mortality was significantly diminished due to “closure of the wounds with buried sutures in the galea.” This operative nuance was then passed from teacher to pupil and has now become one of the tenets of modern neurosurgical practice.

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## Comparison of operative and nonoperative management of spinal epidural abscess: a retrospective review of clinical and laboratory predictors of neurological outcome

### Object

Spinal epidural abscess (SEA), once considered a rare occurrence, has showed a rapid increase in incidence over the past 20–30 years. Recent reports have advocated for conservative, nonoperative management of this devastating disorder with appropriate risk stratification. Crucial to a successful management strategy are decisive diagnosis, prompt intervention, and consistent follow-up care. The authors present a review of their institutional experience with operative and nonoperative management of SEA to assess morbidity and mortality and the accuracy of microbiological diagnosis.

### Methods

A retrospective analysis of patient charts, microbiology reports, operative records, and radiology reports was performed on all cases involving patients admitted with the diagnosis of SEA between July 1998 and May 2009.

### Results

Seventy-seven cases were reviewed (median patient age 51.4 years, range 17–78 years). Axial pain was the most common presenting symptom (67.5% of cases). Presenting signs included focal weakness (55.8%), radiculopathy (28.6%), and myelopathy (5.2%). Abscesses were localized to the lumbar, thoracic, and cervical spine, respectively, in 39 (50.6%), 20 (26.0%), and 18 (23.4%) of the patients. Peripheral blood cultures were negative in 32 (45.1%) of 71 patients. Surgical site or interventional biopsy cultures were diagnostic in 52 cases (78.8%), with concordant blood culture results in 36 (60.0%). Methicillin-resistant Staphylococcus aureus (MRSA) was the most frequent isolate in 24 cases (31.2%). The mean time from admission to surgery was 5.5 days (range 0–42 days; within 72 hours in 66.7% of cases). Outcome data were available in 72 cases. At discharge, patient condition had improved or resolved in 57 cases (79.2%), improved minimally in 6 (8.3%), and showed no improvement or worsening in 9 (12.5%). Patient age and premorbid weakness were the only factors found to be significantly associated with outcome (p = 0.04 and 0.012, respectively).

### Conclusions

These results strongly support immediate surgical decompression combined with appropriately tailored antibiotic therapy for the treatment of symptomatic SEA presenting with focal neurological deficit. The nonsuperiority discovered in other patient subsets may be due to allocation biases between surgically treated and nonsurgically treated cohorts. The present data demonstrate the accuracy of peripheral blood culture for the prediction of causative organisms and confirm patient age as a predictor of outcomes.

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## Dr. Otto “Tiger” Freer: inventor and innovator

Every neurosurgeon develops his or her own standard approach to common intracranial pathologies in terms of the order in which different stages are performed and which instruments are used to perform individual tasks. The majority of the basic steps in performing a craniotomy are learned through repetition and practice during residency training. Significant amounts of energy are devoted to mastering technical skills and developing an operative rhythm. What often receives little attention is the historical origin of the instruments that make the work possible. The Freer elevator represents a particularly interesting example. To people unfamiliar with the accomplishments of turn-of-the-century laryngologist Otto “Tiger” Freer, it can be assumed that the name of the instrument in one's hand is simply named for what it can do, that is, to “free” the nasal mucosa from the bony and cartilaginous septum during the transsphenoidal approach. The technique this master surgeon spent his life and career perfecting is now repeated almost daily by skull base neurosurgeons approaching pathologies from the inferior frontal lobe to the foramen magnum. In reviewing his life and work, the authors of this paper discovered an interesting creative process that led to the design of the eponymous instrument. Additionally, they discovered important advances toward the development of the transnasal approach and in our understanding of the anterior skull base. They present a historical perspective on the life and accomplishments of Dr. Freer and the ubiquitous surgical instrument that he invented and popularized.

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## Occult tumors presenting with negative imaging: analysis of the literature

### Object

Some patients presenting with neurological symptoms and normal findings on imaging studies may harbor occult brain tumors that are undetectable on initial imaging. The purpose of this study was to analyze the cases of occult brain tumors reported in the literature and to determine their modes of presentation and time to diagnosis on imaging studies.

### Methods

A review of the literature was performed using PubMed. The authors found 15 articles reporting on a total of 60 patients with occult tumors (including the authors' illustrative case).

### Results

Seizures were the mode of initial presentation in a majority (61.7%) of patients. The initial imaging was CT scanning in 55% and MRI in 45%. The mean time to diagnosis for occult brain tumors was 10.3 months (median 4 months). The time to diagnosis (mean 7.5 months, median 3.2 months) was shorter (p = 0.046) among patients with seizures. Glioblastoma multiforme (GBM) was found more frequently among patients with seizures (67.6% vs 34.8%, p = 0.013). The average time to diagnosis of GBM was shorter than the time to diagnosis of other tumors; the median time to diagnosis was 3.2 months for GBM and 6 months for other tumors (p = 0.04). There was no predilection for side or location of occult tumors. In adult patients, seizures may be predictive of left-sided tumors (p = 0.04).

### Conclusions

Based on the results of this study, the authors found that in patients with occult brain tumors, the time to diagnosis is shorter among patients with seizures and also among those with GBM.

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## Repair of middle fossa cerebrospinal fluid leaks using a novel combination of materials: technical note

### Object

Methods for repairing middle fossa CSF (MFCSF) leaks have varied and yielded mixed results. The objective of this study was to evaluate the safety and durability of the authors' repair technique using a novel combination of 3 synthetic materials.

### Methods

The authors performed a retrospective case review of patients treated for CSF leaks between January 2009 and September 2011. Eight patients were found to have undergone middle fossa craniotomies for CSF leaks. Inclusion criteria for the study included age greater than 18 years, neuroimaging-documented temporal bone defect, and symptoms consistent with CSF leaks or gross CSF otorrhea. Seven patients, 3 men and 4 women, met the inclusion criteria, and their charts were reviewed. Hydroxyapatite cement, collagen-based dural substitute matrix, and polyethylene glycol hydrogel sealant were used in all patients for the repair.

### Results

In all patients the MFCSF leaks were successfully repaired. Initial presenting symptoms included CSF otorrhea in 4 patients (57.1%), hearing loss in 3 (42.9%), and CSF rhinorrhea in 1 (14.3%). The mean follow-up duration was 12 months (range 5–33 months). In 1 patient an epidural hematoma developed at the operative site on postoperative Day 2, and in another patient a superficial wound dehiscence occurred on postoperative Day 48. During the follow-up period, the authors found no evidence of wound infections, neurovascular damage, or CSF leakage requiring reoperation.

### Conclusions

The middle fossa approach involving a combination of hydroxyapatite cement, collagen-based dural substitute matrix, and polyethylene glycol hydrogel sealant is a safe, effective method for repairing MFCSF leaks. The combination of synthetic materials provides an alternative to existing materials for skull base surgeons.

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## Vagal nerve stimulation for the treatment of medically refractory epilepsy: a review of the current literature

### Object

The authors conducted a study to evaluate the published results of vagal nerve stimulation (VNS) for medically refractory seizures according to evidence-based criteria.

### Methods

The authors performed a review of available literature published between 1980 and 2010. Inclusion criteria for articles included more than 10 patients evaluated, average follow-up of 1 or more years, inclusion of medically refractory epilepsy, and consistent preoperative surgical evaluation. Articles were divided into 4 classes of evidence according to criteria established by the American Academy of Neurology.

### Results

A total of 70 publications were reviewed, of which 20 were selected for review based on inclusion and exclusion criteria. There were 2 articles that provided Class I evidence, 7 that met criteria for Class II evidence, and 11 that provided Class III evidence.

The majority of evidence supports VNS usage in partial epilepsy with a seizure reduction of 50% or more in the majority of cases and freedom from seizure in 6%–27% of patients who responded to stimulation. High stimulation with a gradual increase in VNS stimulation over the first 6 weeks to 3 months postoperatively is well supported by Class I and II data. Predictors of positive response included absence of bilateral interictal epileptiform activity and cortical malformations.

### Conclusions

Vagal nerve stimulation is a safe and effective alternative for adult and pediatric populations with epilepsy refractory to medical and other surgical management.