Philipp Hendrix

Spinal diffusion tensor imaging: a comprehensive review with emphasis on spinal cord anatomy and clinical applications.

Magnetic resonance imaging technology allows for in vivo visualization of fiber tracts of the central nervous system using diffusion‐weighted imaging sequences and data processing referred to as “diffusion tensor imaging” and “diffusion tensor tractography.” While protocols for high‐fidelity diffusion tensor imaging of the brain are well established, the spinal cord has proven a more difficult target for diffusion tensor methods. Here, we review the current literature on spinal diffusion tensor imaging and tractography with special emphasis on neuroanatomical correlations and clinical applications. Clin. Anat. 28:88–95, 2015.

External ventricular drain placement in the intensive care unit versus operating room: Evaluation of complications and accuracy

OBJECTIVE External ventricular drain (EVD) placement is a common neurosurgical procedure performed in both the intensive care unit (ICU) and operating room (OR). The optimal setting for EVD placement in regard to safety and accuracy of placement is poorly defined. METHODS A retrospective chart review was performed on 150 consecutive patients who underwent EVD placement at a tertiary care center from January of 2013 to February of 2014. Clinical and radiographic data were obtained and used to compare safety and accuracy of placement between EVDs placed in the ICU versus OR. RESULTS One hundred and thirty eight patients were evaluated. Complications (hemorrhage, infection, non-functional drain) occurred in 21.5% of ICU placements and 6.7% of OR placements (p = 0.028). Grade 1, 2, and 3 placements occurred in 67.7%, 25.8%, and 6.5% of ICU placements, respectively, versus 55.6%, 42.2%, and 2.2% of OR placements (p = 0.258). No patient who received pre-placement antibiotics suffered a ventriculostomy associated infection (VAI). CONCLUSION Patients who underwent ventriculostomy placement in the ICU differed in important ways (i.e. indication for placement and the administration of pre-procedure prophylactic antibiotics) from patients treated in the OR. However, the available data suggests that complications of hemorrhage, infection, and non-functional drains may be mitigated by ventriculostomy placement in the OR.

Arterial supply of the lower cranial nerves: A comprehensive review

The lower cranial nerves receive their arterial supply from an intricate network of tributaries derived from the external carotid, internal carotid, and vertebrobasilar territories. A contemporary, comprehensive literature review of the vascular supply of the lower cranial nerves was performed. The vascular supply to the trigeminal, facial, vestibulocochlear, glossopharyngeal, vagus, spinal accessory, and hypoglossal nerves are illustrated with a special emphasis on clinical issues. Frequently the external carotid, internal carotid, and vertebrobasilar territories all contribute to the vascular supply of an individual cranial nerve along its course. Understanding of the vasculature of the lower cranial nerves is of great relevance for skull base surgery. Clin. Anat. 27:108–117, 2014.

Neurocognitive status in patients with newly-diagnosed brain tumors in good neurological condition: The impact of tumor type, volume, and location

OBJECTIVE Neurocognitive function is of great importance in patients with brain tumors. Even patients in good neurological condition may suffer from neurocognitive dysfunction that affects their daily living. The purpose of the present study was to identify risk factors for neurocognitive dysfunction in patients suffering from common supratentorial brain tumors with minor neurological deficits. METHODS A prospective study evaluating neurocognitive dysfunction in patients with a newly-diagnosed brain tumor in good neurological condition was performed at a major German academic institution. Patients underwent extensive neurocognitive testing assessing perceptual speed, executive function, visual-spatial and verbal working memory, short- and long-term memory, verbal fluency, fluid intelligence, anxiety, and depression. For each patient, a healthy control was pair-matched based on age, sex, handedness, and profession. RESULTS A total of 46 patients and 46 healthy controls underwent neurocognitive testing. Patients suffered from glioblastoma multiforme (10), cerebral metastasis (10), pituitary adenoma (13), or meningioma (13). There was neither any difference in age, educational level, fluid intelligence, neurological deficits, and anxiety nor in any depression scores between tumor subgroups. Overall, neurocognitive performance was significantly worse in patients compared to healthy controls. Larger tumor volume, frontal location, and left/dominant hemisphere were associated with worse executive functioning and verbal fluency. Additionally, larger tumors and left/dominant location correlated with impairments on perceptual speed tasks. Frontal tumor location was related to worse performance in visual-spatial and short- and long-term memory. Tumor type, clinical presentation, and patient self-awareness were not associated with specific neurocognitive impairments. CONCLUSIONS Patients suffering from newly-diagnosed brain tumors presenting in good neurological condition display neurocognitive impairments in various domains. Larger tumor volumes, frontal location, and left/dominant hemisphere are important predictors for potential neurocognitive deficits. Tumor type, clinical presentation, or self-awareness are less significant at the time of diagnosis.

Relationship between pharyngitis and peri‐odontoid pannus: A new etiology for some Chiari I malformations?

The pathophysiology underlying Chiari I malformations (CIMs) provides room for debate with several theories attempting to address this issue. We retrospectively reviewed many of our past patients with pediatric CIMs (specifically, those with peri‐odontoid pannus), and present a hypothesis for the development of the malformation in some of said patients. Our experience with the pediatric CIM has shown that almost 1 in 20 patients who present with symptoms is found to have a peri‐odontoid pannus. These masses ranged in size from 4 to 11 mm in diameter. Forty percent had a history of clinically significant pharyngitis or pharyngeal abscess. Pannus formation around the dens (odontoid) resulted in ventral compression of the craniocervical junction in each of these patients. Highlighting the hypermobility that causes such lesions, following fusion, the pannus and symptoms in several patients were diminished. Impairment of normal cerebrospinal fluid circulation out of the fourth ventricle and across the craniocervical junction appears to be a plausible endpoint in this discussion and a suitable explanation for some patients with CIM. Still, the mechanisms by which cerebrospinal fluid circulation is compromised may be variable and are not well understood. This is the first study dedicated to the evaluation of pannus formation in the CIM population. We hypothesize that pharyngeal inflammatory conditions contribute to the formation and progression of hindbrain herniation in a small subset of patients with CIMs. Clin. Anat. 28:602–607, 2015.

Arterial supply of the upper cranial nerves: A comprehensive review: Arterial Supply Cranial Nerves

The arterial supply to the upper cranial nerves is derived from a complex network of branches derived from the anterior and posterior cerebral circulations. We performed a comprehensive literature review of the arterial supply of the upper cranial nerves with an emphasis on clinical considerations. Arteries coursing in close proximity to the cranial nerves regularly give rise to small vessels that supply the nerve. Knowledge of the arteries supplying the cranial nerves is of particular importance during surgical approaches to the skull base. Clin. Anat. 27:1159–1166, 2014.

Preoperative Embolization of Spinal Tumors: A Systematic Review and Meta-Analysis

BACKGROUND Spinal tumors are referred for preoperative embolization to minimize intraoperative blood loss and facilitate surgical resection. OBJECTIVE To perform a systematic review and meta-analysis and provide comprehensive data on embolization technique, efficacy, and complications. METHODS A systematic review of PubMed articles was performed with the following inclusion criteria: original studies, studies of ≥ 10 patients (except Onyx because of the scarcity of available data), embolization through vascular access, and reporting of the embolic agent used. In addition, the manuscript needed to contain at least 1 of the following variables: demographics, tumor type, location, vascularity, degree of devascularization, complications, time to operation, type of operation, estimated blood loss (EBL), and use of blood transfusion. RESULTS Thirty-seven studies with a total of 1305 patients met inclusion criteria. Renal cell carcinoma was the most commonly embolized tumor, comprising 47.4% (95% confidence interval [95% CI] 39.4-55.4) of all tumor embolizations. The rate of complete devascularization for all tumor types was 68.3% (95% CI 60.0-76.6). There was a significant decrease in operative EBL in more recently published studies compared with earlier studies; however, the rate of complete embolization remained stable. Polyvinyl alcohol and Onyx were associated with similar EBL and rates of complete embolization. The overall complication rate was 3.1% (95% CI 1.2-4.9). CONCLUSIONS The rapid evolution of neurointervention and spinal tumor embolization has made scientific inquiry and definitive conclusion on the safety and efficacy of the practice difficult. The data supporting the procedure are fragmented and largely based on a multitude of retrospective studies that use varying techniques. Review of the available literature support embolization of spinal tumors as a safe and efficacious treatment adjunct before surgery.

Preoperative navigated transcranial magnetic stimulation in patients with motor eloquent lesions with emphasis on metastasis

Navigated transcranial magnetic stimulation (nTMS) is a frequently used, non‐invasive method to map the motor cortex. It is of great value in the preoperative workup of patients that suffer from motor eloquent brain lesions. Here, we present a single‐center experience using preoperative nTMS in cortical motor eloquent lesions with emphasis on metastasis. All patients that underwent preoperative nTMS between June 2013 and January 2016 were evaluated. A total of 61 patients underwent nTMS before undergoing surgery for a motor eloquent brain lesion. Patients suffered from cerebral metastasis (23), glioblastoma (16), high grade glioma WHO III (4), low grade glioma WHO II (4), lymphoma (2), meningioma (8), cavernous hemangioma (3), or arteriovenous malformation (1). Thirty patients (49.2%) presented with a preoperative motor deficit. One week after surgery, paresis had resolved or improved in 56.7% of the patients. Out of the patients with postoperative paresis, 89.5% experienced an improvement of motor status at follow‐up. All metastatic lesions were completely resected compared to 78.9% of non‐metastatic lesions (P = 0.02). Only 4.3% of patients with a metastatic lesion, but 26.3% of patients with a non‐metastatic lesion experienced deterioration of motor function after surgery (P = 0.04). Preoperative nTMS is suitable for mapping of a variety of motor eloquent brain lesions resulting in favorable neurological outcome. Particularly in metastatic motor eloquent lesion, motor function appears to be preserved after surgery. Clin. Anat. 29:925–931, 2016.

Cognitive function surrounding resection of nonfunctioning pituitary adenomas with suprasellar extension: A prospective matched-control study

OBJECTIVE Patients suffering from pituitary adenomas may experience cognitive dysfunctions due to hormonal imbalance or suprasellar tumor extension displacing neural structures. Progressively enlarging or symptomatic nonfunctioning pituitary adenomas with suprasellar extension are frequently resected. The literature on neurocognitive performance surrounding resection of these lesions is sparse. METHODS A prospective matched-control study was conducted to investigate the impact of nonfunctioning pituitary adenomas with suprasellar extension on preoperative and postoperative cognitive performance. Controls were matched for age, sex, handedness, education, and profession. The neurocognitive test battery included perceptual speed, executive function, visual-spatial and verbal working memory, short- and long-term memory, verbal fluency, fluid intelligence, anxiety, and depression. RESULTS Ten patients and 10 healthy controls were matched. Median suprasellar tumor extension scored 8mm, compression of frontal lobe parenchyma was present in all cases. Median sagittal tumor diameter was 21mm. Preoperatively, patients scored worse in perceptual speed and short-term memory tasks. All patients underwent surgical resection either through a transnasal, transsphenoidal approach or a supraorbital frontolateral keyhole approach. The short-term memory deficit disappeared one week after surgery. Perceptual speed recovered within two months after surgical therapy. None of the patients experienced worsening of cognitive function. Routine postoperative imaging at six months did not reveal displacement of neural structures or surgery-related complications in any of the patients. CONCLUSION Patients suffering from nonfunctioning pituitary adenomas with suprasellar extension may experience preoperative impairments in some neurocognitive domains that resolve within two months after surgery. The risk for cognitive deterioration with surgery appears to be low.

Preoperative navigated transcranial magnetic stimulation and tractography in transparietal approach to the trigone of the lateral ventricle

OBJECTIVE Eloquent neural structures including white matter tracts surround the trigone of the lateral ventricle. Surgical resection of trigonal tumors via the transparietal approach may cause neurological deterioration depending on the trajectory. METHODS The authors retrospectively reviewed patients with trigonal tumors that underwent combined preoperative navigated transcranial magnetic stimulation (nTMS) and optic radiation tractography to guide a transparietal approach towards the trigone. RESULTS Five patients underwent preoperative nTMS motor mapping, rTMS language mapping, nTMS-derived corticospinal tract tractography, and optic radiation tractography. The information was used to select the optimal trajectory for a transparietal approach and for intraoperative neuronavigation. Four patients underwent surgical resection. None of them experienced a new permanent deficit. CONCLUSION Combination of preoperative nTMS and optic radiation tractography facilitates the identification of the optimal parietal trajectory towards the trigone. It allows for sparing of visual and motor pathways as well as cortical language areas.