Dennis Malkasian

Endonasal versus supraorbital keyhole removal of craniopharyngiomas and tuberculum sellae meningiomas.

OBJECTIVE Endonasal and supraorbital “eyebrow” craniotomies are increasingly being used to remove craniopharyngiomas and tuberculum sellae meningiomas. Herein, we assess the relative advantages, disadvantages, and selection criteria of these 2 keyhole approaches. METHODS All consecutive patients who had endonasal or supraorbital removal of a craniopharyngioma or tuberculum sellae meningioma were analyzed. RESULTS Of 43 patients, 22 had a craniopharyngioma (18 endonasal, 4 supraorbital), and 21 had a meningioma (12 endonasal, 7 supraorbital, 2 both routes); 33% had prior surgery. Craniopharyngiomas were primarily retrochiasmal in location in 78% of endonasal cases versus 25% of supraorbital cases (P = 0.08). Meningiomas were larger when approached by the supraorbital route versus the endonasal route (33 ± 10 versus 25 ± 8 mm, respectively; P = 0.008). Endoscopy was used in 84% of endonasal approaches and in 31% of supraorbital approaches (P = 0.001). Of patients having first-time surgery for a craniopharyngioma (n = 14) or meningioma (n = 15), total/near total removal was achieved in 83% and 80% of patients by the endonasal route and in 50% and 80% of patients by the supraorbital route, respectively. Vision improved in 87% and 70% of patients who had surgery by an endonasal versus supraorbital route, respectively (P = 0.3). Visual deterioration occurred in 2 patients with meningiomas, 1 by endonasal (7%), and 1 by supraorbital (11%) removal. The endonasal approach was associated with a higher rate of postoperative cerebrospinal fluid leaks (16 versus 0%; P = 0.3), 4 of 5 of which occurred in patients with meningioma. CONCLUSION The endonasal route is preferred for removal of most retrochiasmal craniopharyngiomas, whereas the supraorbital route is recommended for meningiomas larger than 30 to 35 mm or with growth beyond the supraclinoid carotid arteries. For smaller midline tumors, either approach can be used, depending on surgeon experience and tumor anatomy. Compared with traditional craniotomies, the major limitation of both approaches is a narrow surgical corridor. The endonasal approach has the added challenges of restricted lateral suprasellar access, a greater need for endoscopy, and a more demanding cranial base repair.

Avoidance of carotid artery injuries in transsphenoidal surgery with the Doppler probe and micro-hook blades.

OBJECTIVE Internal carotid artery (ICA) injury during sellar dural opening is a potentially catastrophic complication of transsphenoidal surgery. We describe two ICA injuries that occurred early in our endonasal transsphenoidal experience. We then describe our subsequent protocol to prevent this complication in which we use the Doppler probe for carotid localization and micro-hook blades for lateral dural opening. METHODS All patients undergoing endonasal tumor removal were analyzed since beginning this approach in 1998. Of 631 procedures (585 patients), three patients sustained an ICA injury. RESULTS In the first 114 procedures (105 patients) in which the Doppler probe was not used and hook blades were used infrequently, two (1.8%) ICA injuries occurred. In both cases, a right nostril approach was used and the left ICA was punctured on dural opening with a straight scalpel; both patients recovered without neurological sequelae. In the subsequent 517 procedures in which the Doppler probe and hook blades were used in all cases, one (0.19%) probable ICA injury occurred during an attempted removal of a cavernous sinus schwannoma, although there was no angiographic evidence of vascular injury. There were no ICA or other intracranial vascular injuries in the last 510 procedures for tumors not solely confined to the cavernous sinus. CONCLUSION Cavernous carotid localization with the Doppler probe before dural opening and angled hook blades for lateral dural opening can help minimize the risk of ICA injury and are recommended for all transsphenoidal operations. Because of the wider contralateral exposure provided by the endonasal approach, the ICA contralateral to the nostril of approach is at higher risk of injury on dural opening.

Cerebral arteriovenous malformations. Part 2: physiology

OBJECT The scientific understanding of the nature of arteriovenous malformations (AVMs) in the brain is evolving. It is clear from current work that AVMs can undergo a variety of phenomena, including growth, remodeling, and/or regression-and the responsible processes are both molecular and physiological. A review of these complex processes is critical to directing future therapeutic approaches. The authors performed a comprehensive review of the literature to evaluate current information regarding the genetics, pathophysiology, and behavior of AVMs. METHODS A comprehensive literature review was conducted using PubMed to reveal the angioarchitecture and cerebral hemodynamics of AVMS as they relate to lesion development. RESULTS Feeding artery pressures, brain AVM compartmentalization, venous drainage, flow phenomena, and vascular steal are discussed. CONCLUSIONS The dynamic nature of brain AVMs is at least in part attributable to hemodynamic and flow-related phenomena. These forces acting on an evolving structure are critical to understanding the challenges in endovascular and surgical therapy. As knowledge in this field continues to progress, the natural history and predicted behavior of these AVMs will become more clearly elucidated.

Cerebral arteriovenous malformations. Part 1: cellular and molecular biology.

OBJECT The scientific understanding of the nature of arteriovenous malformations (AVMs) in the brain is evolving. It is clear from current work that AVMs can undergo a variety of phenomena, including growth, remodeling, and/or regression-and the responsible processes are both molecular and physiological. A review of these complex processes is critical to directing future therapeutic approaches. The authors performed a comprehensive review of the literature to evaluate current information regarding the genetics, pathophysiology, and behavior of AVMs. METHODS A comprehensive literature review was conducted using PubMed to reveal the molecular biology of AVMs as it relates to their complex growth and behavior patterns. RESULTS Growth factors involved in AVMs include vascular endothelial growth factor, fibroblast growth factor, transforming growth factor beta, angiopoietins, fibronectin, laminin, integrin, and matrix metalloproteinases. Conclusions Understanding the complicated molecular milieu of developing AVMs is essential for defining their natural history. Growth factors, extracellular matrix proteins, and other molecular markers will be the key to unlocking novel targeted drug treatments for these brain malformations.

Suboptimal sphenoid and sellar exposure: a consistent finding in patients treated with repeat transsphenoidal surgery for residual endocrine-inactive macroadenomas.

OBJECTIVE:In a series of patients with residual endocrine-inactive macroadenomas who underwent repeat surgery, we assess possible reasons for prior subtotal removal, reoperative success, complication rates, and patient impressions. METHODS:All patients were identified who had a prior subtotal removal of an endocrine-inactive macroadenoma and were reoperated on for residual sellar tumor via an endonasal approach. RESULTS:Over 6 years, of 188 consecutive patients with endocrine-inactive adenomas, 30 (16%) had repeat surgery (age, 15–77 yr; median interval between surgeries, 25 mo; median follow-up, 20 mo). Maximal tumor diameter averaged 2.4 ± 0.9 cm. At reoperation, a suboptimal bony exposure was seen in all 30 patients: at the sphenoid keel, the sella, or both in 97, 93, and 90% of patients, respectively. Cavernous sinus invasion was seen in 16 (53%) patients and a fibrous/rubbery consistency in 12 (40%). Gross total tumor removal was achieved in 17 (57%) patients, including 12 of 14 (86%) with noninvasive tumors and 5 of 16 (31%) with invasive tumors, (P < 0.01). All six fibrous/rubbery but noninvasive tumors were totally removed. Of 16 patients with preoperative visual loss, 15 (94%) improved. Complications included one each of cerebrospinal fluid leak, delayed sinusitis, and new hypothyroidism. In 17 patients with prior sublabial surgery who completed questionnaires, the second (endonasal) surgery was associated with an easier recovery, less pain, and better nasal airflow in 82, 88, and 93%, respectively (P < 0.0001). CONCLUSION:In patients with residual sellar endocrine-inactive adenomas, a suboptimal opening at the sphenoid keel or sella at the first surgery and a high proportion of fibrous/rubbery tumors likely contributed to prior subtotal removal of otherwise accessible tumor. With a wider exposure, most noninvasive tumors can be totally removed, whereas invasive tumors can be effectively debulked. An endonasal reoperation is well tolerated with a low complication rate.

The role of modern imaging modalities on deep brain stimulation targeting for mental illness

INTRODUCTION The reversible nature of deep brain stimulation (DBS) brought renewed interest on surgery to medically intractable mental illnesses. The explosion of anatomical and functional imaging has allowed the development of new potential targets and the understanding of historical targets. METHODS Fifteen patients undergoing stereotactic surgery for movement disorders, at UCLAs interventional MRI operating-room, were studied with fiber tracking. Stereotactic targets and fiber tracking were determined on MRIs using the Schaltenbrand-Wahren atlas for definition in the iPlan software. Cingulate, subcaudate, BA25/CgWM, amygdala, posterior hypothalamus, orbitofrontal cortex, nucleus accumbens, anterior limb of the internal capsule and dorsomedial thalamus were studied. DTI parameters used ranged from 10 to 20mm for voxel size in the x/y/z planes, fiber length was kept constant at 36 mm, and fractional anisotropy (FA) threshold varied from 0.20 to 0.25. RESULTS Reliable interconnectivity of targets were determined with DTI and related to PET imaging. Mental illness targets were observed with functional and fiber tract maps. This confirmation yields reliability to DTI imaging in order to determine novel targets and enhance the understanding of areas not well understood. CONCLUSIONS Currently available imaging techniques, the reversibility of DBS to modulate targets promises to bring a brighter future for surgery of mental illness.

Contralateral conjugate eye deviation during deep brain stimulation of the subthalamic nucleus

OBJECT Deep brain stimulation of the subthalamic nucleus (STN) in patients with Parkinson disease is often very effective for treatment of debilitating motor symptoms. Nevertheless, the small size of the STN and its proximity to axonal projections results in multiple side effects during high-frequency stimulation. Contralateral eye deviation is produced in a small percentage of patients, but the precise mechanism of this side effect is at present poorly understood. METHODS Contralateral eye deviation was produced by high-frequency stimulation of 22 contact sites in nine patients undergoing deep brain stimulation of the STN. The precise locations of these contacts were calculated and compiled in order to locate the stimulated structure responsible for eye deviation. RESULTS The mean x, y, and z coordinates associated with contralateral eye deviation were found to be 11.57, 2.03, and 3.83 mm lateral, posterior, and inferior to the anterior commissure-posterior commissure midpoint, respectively. The point described by these coordinates is located within the lateral anterosuperior border of the STN. CONCLUSIONS Given that stimulation of frontal eye field cortical regions produces similar contralateral conjugate eye deviation, these results are best explained by electrical current spread to nearby frontal eye field axons coursing lateral to the STN within the internal capsule. Thus, placement of the implanted electrode in a more medial, posterior, and inferior position may bring resolution of these symptoms by reducing the amount of current spread to internal capsule ax-

Stereotactic coordinates associated with facial musculature contraction during high-frequency stimulation of the subthalamic nucleus

OBJECT High-frequency stimulation of the subthalamic nucleus (STN) in patients with parkinsonian symptoms is often used to ameliorate debilitating motor symptoms associated with this condition. However, individual variability in the shape and orientation of this relatively small nucleus results in multiple side effects related to the spread of electrical current to surrounding structures. Specifically, contraction of the muscles of facial expression is noted in a small percentage of patients, although the precise mechanism remains poorly understood. METHODS Facial muscle contraction was triggered by high-frequency stimulation of 49 contacts in 18 patients undergoing deep brain stimulation of the STN. The mean coordinates of these individual contacts relative to the anterior commissure-posterior commissure midpoint (also called the midcommissural point) were calculated to determine the location or structure(s) most often associated with facial contraction during physiological macrostimulation. RESULTS The x, y, and z coordinates associated with contraction of the facial musculature were found to be 11.52, 1.29, and 1.15 mm lateral, posterior, and inferior to the midcommissural point, respectively. This location, along the lateral-anterior-superior border of the STN, may allow for the spread of electrical current to the fields of Forel, zona incerta, and/or descending corticospinal/corticobulbar tracts. Because stimulation of corticobulbar tracts produces similar findings, these results are best explained by the spread of electrical current to nearby internal capsule axons coursing lateral to the STN. CONCLUSIONS Thus, if intraoperative deep brain stimulation lead testing results in facial musculature contraction, placement of the electrode in a more medial, posterior position may reduce the amount of current spread to corticobulbar fibers and resolve this side effect.

A Short Trapezoidal Speculum for Suprasellar and Infrasellar Exposure in Endonasal Transsphenoidal Surgery

OBJECTIVE A key limitation of the transsphenoidal approach for suprasellar and infrasellar lesions is restricted exposure. Microscope and endoscope-assisted procedures have traditionally used an oval-shaped speculum, the distal end of which restricts superior and inferior visualization. To improve visualization and use of the endoscope, shorter specula, with a trapezoidal distal end, were designed. METHODS The new specula have a working length of 60 mm. The proximal 20-mm segment is oval-shaped to conform to the nostril; the middle 20-mm segment has vertically oriented blades; and the distal 20-mm segment transitions to a trapezoidal orientation, with the distal blades angled 15 degrees upward and outward on the suprasellar speculum, or 15 degrees downward and outward on the infrasellar speculum. Both specula have a 5-degree distal outward flare. The upward-angled trapezoidal 60-mm speculum was compared with 70- and 80-mm oval specula in a transsphenoidal clay model. A pen light was projected from the nasal speculum end to a target 100 mm away using a blade opening width of 16 mm. Line drawings were made to quantify the impact of speculum length on the horizontal angle of exposure. The clinical utility of the trapezoidal specula was also assessed. RESULTS In the model, the 60-mm upward-angled trapezoidal speculum yielded a surface area illumination of 759 mm2, as compared with 579 and 432 mm2 with the 70-and 80-mm oval specula, an increase in exposure of 31 and 76%, respectively. In the line drawings, the 60-mm speculum provided a horizontal angle of exposure of 30 degrees, as compared with 26 and 23 degrees for the 70- and 80-mm specula, an increase of 17 and 33%, respectively. In patients, provided sufficient mucosa and bone are removed from the posterior nasal cavity, the trapezoidal specula provide an expanded working volume that facilitates endoscopy. CONCLUSION Short upward- or downward-angled trapezoidal endonasal specula increase parasellar surface area exposure and the horizontal angle of exposure. Initial clinical experience suggests that reducing the speculum length and eliminating the distal curved blades result in greater instrument maneuverability and enhanced visibility for removing parasellar tumors.

Alzheimer's disease: The role for neurosurgery

Dementia, most commonly caused by Alzheimers disease (AD), affects approximately 35 million people worldwide, with the incidence expected to increase as the population ages. After decades of investigation, AD is now understood to be a complex disease that affects behavior and cognition through several mechanisms: Disrupted neuronal communication, abnormal regional tissue metabolism, and impaired cellular repair. Existing therapies have demonstrated limited efficacy, which has spurred the search for specific disease markers and predictors as well as innovative therapeutic options. Deep brain stimulation (DBS) of the memory circuits is one such option, with early studies suggesting that modulation of neural activity in these networks may improve cognitive function. Encapsulated cell biodelivery (ECB) is a device that delivers nerve growth factor to the cholinergic basal forebrain to potentially improve cognitive decline in AD patients. This review discusses the pathogenesis of AD, novel neuroimaging and biochemical markers, and the emerging role for neurosurgical applications such as DBS and ECB.