Garni Barkhoudarian

The molecular pathophysiology of concussive brain injury.

Concussion or mild traumatic brain injury (mTBI) is a condition that affects hundreds of thousands of patients worldwide. Understanding the pathophysiology of this disorder can help manage its acute and chronic repercussions. Immediately following mTBI, there are several metabolic, hemodynamic, structural, and electric changes that alter normal cerebral function. These alterations can increase the brains vulnerability to repeat injury and long-term disability. This review evaluates current studies from the bench to the bedside of mTBI. Acute and chronic effects of concussion are measured in both animal and clinical studies. Also, the effect of repeat concussions is analyzed. Concussion-induced pathophysiology with regards to glucose metabolism changes, mitochondrial dysfunction, axonal injury, and structural damage are evaluated. Translational studies such as functional magnetic resonance imaging, magnetic resonance spectroscopy and diffusion tensor imaging prove to be effective clinical tools for both prognostic and treatment parameters. Understanding the neurobiology of concussion will lead to development and validation of physiological biomarkers of this common injury. These biomarkers (eg, laboratory tests, imaging, electrophysiology) will then allow for improved detection, better functional assessment and evidence-based return to play recommendations.

Prevalence of Pituitary Hormone Dysfunction, Metabolic Syndrome, and Impaired Quality of Life in Retired Professional Football Players: A Prospective Study

Hypopituitarism is common after moderate and severe traumatic brain injury (TBI). Herein, we address the association between mild TBI (mTBI) and pituitary and metabolic function in retired football players. Retirees 30-65 years of age, with one or more years of National Football League (NFL) play and poor quality of life (QoL) based on Short Form 36 (SF-36) Mental Component Score (MCS) were prospectively enrolled. Pituitary hormonal and metabolic syndrome (MetS) testing was performed. Using a glucagon stimulation test, growth hormone deficiency (GHD) was defined with a standard cut point of 3 ng/mL and with a more stringent body mass index (BMI)-adjusted cut point. Subjects with and without hormonal deficiency (HD) were compared in terms of QoL, International Index of Erectile Function (IIEF) scores, metabolic parameters, and football career data. Of 74 subjects, 6 were excluded because of significant non-football-related TBIs. Of the remaining 68 subjects (mean age, 47.3±10.2 years; median NFL years, 5; median NFL concussions, 3; mean BMI, 33.8±6.0), 28 (41.2%) were GHD using a peak GH cutoff of <3 ng/mL. However, with a BMI-adjusted definition of GHD, 13 of 68 (19.1%) were GHD. Using this BMI-adjusted definition, overall HD was found in 16 (23.5%) subjects: 10 (14.7%) with isolated GHD; 3 (4.4%) with isolated hypogonadism; and 3 (4.4%) with both GHD and hypogonadism. Subjects with HD had lower mean scores on the IIEF survey (p=0.016) and trended toward lower scores on the SF-36 MCS (p=0.113). MetS was present in 50% of subjects, including 5 of 6 (83%) with hypogonadism, and 29 of 62 (46.8%) without hypogonadism (p=0.087). Age, BMI, median years in NFL, games played, number of concussions, and acknowledged use of performance-enhancing steroids were similar between HD and non-HD groups. In summary, in this cohort of retired NFL players with poor QoL, 23.5% had HD, including 19% with GHD (using a BMI-adjusted definition), 9% with hypogonadism, and 50% had MetS. Although the cause of HD is unclear, these results suggest that GHD and hypogonadism may contribute to poor QoL, erectile dysfunction, and MetS in this population. Further study of pituitary function is warranted in athletes sustaining repetitive mTBI.

The molecular biology and novel treatments of vestibular schwannomas.

Vestibular schwannomas are histopathologically benign tumors arising from the Schwann cell sheath surrounding the vestibular branch of cranial nerve VIII and are related to the NF2 gene and its product merlin. Merlin acts as a tumor suppressor and as a mediator of contact inhibition. Thus, deficiencies in both NF2 genes lead to vestibular schwannoma development. Recently, there have been major advances in our knowledge of the molecular biology of vestibular schwannomas as well as the development of novel therapies for its treatment. In this article the authors comprehensively review the recent advances in the molecular biology and characterization of vestibular schwannomas as well as the development of modern treatments for vestibular schwannoma. For instance, merlin is involved with a number of receptors including the CD44 receptor, EGFR, and signaling pathways, such as the Ras/raf pathway and the canonical Wnt pathway. Recently, merlin was also shown to interact in the nucleus with E3 ubiquitin ligase CRL4(DCAF1). A greater understanding of the molecular mechanisms behind vestibular schwannoma tumorigenesis has begun to yield novel therapies. Some authors have shown that Avastin induces regression of progressive schwannomas by over 40% and improves hearing. An inhibitor of VEGF synthesis, PTC299, is currently in Phase II trials as a potential agent to treat vestibular schwannoma. Furthermore, in vitro studies have shown that trastuzumab (an ERBB2 inhibitor) reduces vestibular schwannoma cell proliferation. With further research it may be possible to significantly reduce morbidity and mortality rates by decreasing tumor burden, tumor volume, hearing loss, and cranial nerve deficits seen in vestibular schwannomas.

Molecular and physiological responses to juvenile traumatic brain injury: focus on growth and metabolism.

Traumatic brain injury (TBI), one of the most frequent causes of neurologic and neurobehavioral morbidity in the pediatric population, can result in lifelong challenges not only for patients, but also for their families. Survivors of a brain injury experienced during childhood – when the brain is undergoing a period of rapid development – frequently experience unique challenges as the consequences of their injuries are overlaid on normal developmental changes. Experimental studies have significantly advanced our understanding of the mechanisms and underlying molecular underpinnings of the injury response and recovery process following a TBI in the developing brain. In this paper, normal and TBI-related alterations in growth, development and metabolism are comprehensively reviewed in the postweanling/juvenile age range in the rat (postnatal days 21–60). As part of this review, TBI-related changes in gene expression are presented, with a focus on the injury-induced alterations related to cerebral growth and metabolism, and discussed in the context of existing literature related to physiological and behavioral responses to experimental TBI. Increasing evidence from the existing literature and from our own gene microarray data indicates that molecular responses related to growth, development and metabolism may play a particularly important role in the injury response and the recovery trajectory following developmental TBI. While gene expression analysis shows many of these changes occur at the level of transcription, a comprehensive review of other studies suggests that the control of metabolic substrates may preferentially be regulated through changes in transporters and enzymatic activity. The interrelation between cellular metabolism and activity-dependent neuroplasticity shows great promise as an area for future study for an optimal translation of experimental data to clinical TBI, with the ultimate goal of guiding therapeutic interventions.

The Molecular Pathophysiology of Concussive Brain Injury – an Update

Concussion, or mild traumatic brain injury (TBI), affects millions of patients worldwide. Understanding the pathophysiology of TBI can help manage its repercussions. The brain is significantly altered immediately following mild TBI because of metabolic, hemodynamic, structural, and electrophysiologic changes. This process affects cognition and behavior and can leave the brain vulnerable for worse injury in the setting of repeat insult. This article is an update of our previously published review, reporting relevant and current studies from the bench to the bedside of mild TBI. Understanding the pathobiology can help prevent and treat mild TBI.

Evaluation of the 3-Dimensional Endoscope in Transsphenoidal Surgery

BACKGROUND: Three-dimensional (3-D) endoscopy is a recent addition to augment the transsphenoidal surgical approach for anterior skull-base and parasellar lesions. We describe our experience implementing this technology into regular surgical practice. OBJECTIVE: Retrospective review of clinical factors and outcomes. METHODS: All patients were analyzed who had endoscopic endonasal parasellar operations since the introduction of the 3-D endoscope to our practice. Over an 18-month period, 160 operations were performed using solely endoscopic techniques. Sixty-five of these were with the Visionsense VSII 3-D endoscope and 95 utilized 2-dimensional (2-D) high-definition (HD) Storz endoscopes. Intraoperative and postoperative findings were analyzed in a retrospective fashion. RESULTS: Comparing both groups, there was no significant difference in total or surgical operating room times comparing the 2-D HD and 3-D endoscopes (239 minutes vs 229 minutes, P = .47). Within disease-specific comparison, pituitary adenoma resection was significantly shorter utilizing the 3-D endoscope (surgical time 174 minutes vs 147 minutes, P = .03). These findings were independent of resident or fellow experience. There was no significant difference in the rate of complication, reoperation, tumor resection, or intraoperative cerebrospinal fluid leaks. Subjectively, the 3-D endoscope offered increased agility with 3-D techniques such as exposing the sphenoid rostrum, drilling sphenoidal septations, and identifying bony landmarks and suprasellar structures. CONCLUSION: The 3-D endoscope is a useful alternative to the 2-D HD endoscope for transnasal anterior skull-base surgery. Preliminary results suggest it is more efficient surgically and has a shorter learning curve. As 3-D technology and resolution improve, it should serve to be an invaluable tool for neuroendoscopy. ABBREVIATION: HD, high definition

Challenges in Linear Accelerator Radiotherapy for Chordomas and Chondrosarcomas of the Skull Base: Focus on Complications

PURPOSE Intracranial chordomas and chondrosarcomas are histologically low-grade, locally invasive tumors that infiltrate the skull base. Currently, consensus therapy includes surgical resection and adjuvant radiotherapy. Radiation delivery is typically limited by the proximity of these tumors to critical skull base structures. METHODS This is a retrospective review of 13 cases of chordomas and 2 cases of chondroid chondrosarcomas of the skull based treated with linear accelerator stereotactic radiotherapy (SRT, n = 10) or stereotactic radiosurgery (SRS, n = 5). The average time to the most recent follow-up visit was 4.5 years. The tumor characteristics, treatment details, and outcomes were recorded. Each radiation plan was reviewed, and the dosage received by the brainstem, optic apparatus, and pituitary was calculated. RESULTS Of the 10 patients treated with SRT, 6 were found to have unchanged or decreased tumor size as determined from radiographic follow-up. Of the 5 patients treated with SRS, 3 were found to have stable or unchanged tumors at follow-up. The complications included 1 SRT patient who developed endocrinopathy, 2 patients (1 treated with SRS and the other with SRT), who developed cranial neuropathy, and 1 SRS patient who developed visual deficits. Additionally, 1 patient who received both SRS and SRT within 2 years for recurrence experienced transient medial temporal lobe radiation changes that resolved. CONCLUSIONS Where proton beam therapy is unavailable, linear accelerator-based SRT or radiosurgery remains a safe option for adjuvant therapy of chordomas and chondrosarcomas of the skull base. The exposure of the optic apparatus, pituitary stalk, and brainstem must be considered during planning to minimize complications. If the optic apparatus is included in the 80% isodose line, it might be best to fractionate therapy. Exposure of the pituitary stalk should be kept to <30 Gy to minimize endocrine dysfunction. Brainstem exposure should be limited to <60 Gy in fractions.

Comparison of sinonasal quality of life and health status in patients undergoing microscopic and endoscopic transsphenoidal surgery for pituitary lesions: a prospective cohort study.

OBJECT Despite the widespread adoption of endoscopic transsphenoidal surgery for pituitary adenomas, the sinonasal quality of life (QOL) and health status in patients who have undergone this technique have not been compared with these findings in patients who have undergone the traditional direct uninostril microsurgical technique. In this study, the authors compared the sinonasal QOL and patient-reported health status after use of these 2 surgical techniques. METHODS The study design was a nonblinded prospective cohort study. Adult patients with sellar pathology and planned transsphenoidal surgery were screened at 4 pituitary centers in the US between October 2011 and August 2013. The primary end point of the study was postoperative patient-reported sinonasal QOL as measured by the Anterior Skull Base Nasal Inventory-12 (ASK Nasal-12). Supplementary end points included patient-reported health status estimated by the 8-Item Short Form Health Survey (SF-8) and EuroQol (EQ)-5D-5L instruments, and sinonasal complications. Patients were followed for 6 months after surgery. RESULTS A total of 301 patients were screened and 235 were enrolled in the study. Of these, 218 were analyzed (111 microsurgery patients, 107 endoscopic surgery patients). Demographic and tumor characteristics were similar between groups (p ≥ 0.12 for all comparisons). The most common complication in both groups was sinusitis (7% in the microsurgery group, 13% in the endoscopic surgery group; p = 0.15). Patients treated with the endoscopic technique were more likely to have postoperative nasal debridements (p < 0.001). The ASK Nasal-12 and SF-8 scores worsened substantially for both groups at 2 weeks after surgery, but then returned to baseline at 3 months. At 3 months after surgery, patients treated with endoscopy reported statistically better sinonasal QOL compared with patients treated using the microscopic technique (p = 0.02), but there were no significant differences at any of the other postoperative time points. CONCLUSIONS This is the first multicenter study to examine the effect of the transsphenoidal surgical technique on sinonasal QOL and health status. The study showed that surgical technique did not significantly impact these patient-reported measures when performed at high-volume centers. Clinical trial registration no.: NCT01504399 ( clinicaltrials.gov ).

The expanding role of the endonasal endoscopic approach in pituitary and skull base surgery: A 2014 perspective.

Background: The past two decades have been the setting for remarkable advancement in endonasal endoscopic neurosurgery. Refinements in camera definition, surgical instrumentation, navigation, and surgical technique, including the dual surgeon team, have facilitated purely endonasal endoscopic approaches to the majority of the midline skull base that were previously difficult to access through the transsphenoidal microscopic approach. Methods: This review article looks at many of the articles from 2011 to 2014 citing endonasal endoscopic surgery with regard to approaches and reconstructive techniques, pathologies treated and outcomes, and new technologies under consideration. Results: Refinements in approach and closure techniques have reduced the risk of cerebrospinal fluid leak and infection. This has allowed surgeons to more aggressively treat a variety of pathologies. Four main pathologies with outcomes after treatment were identified for discussion: pituitary adenomas, craniopharyngiomas, anterior skull base meningiomas, and chordomas. Within all four of these tumor types, articles have demonstrated the efficacy, and in certain cases, the advantages over more traditional microscope-based techniques, of the endonasal endoscopic technique. Conclusions: The endonasal endoscopic approach is a necessary tool in the modern skull base surgeons armamentarium. Its efficacy for treatment of a wide variety of skull base pathologies has been repeatedly demonstrated. In the experienced surgeons hands, this technique may offer the advantage of greater tumor removal with reduced overall complications over traditional craniotomies for select tumor pathologies centered near the midline skull base.

Refractory pituitary granulomatosis with polyangiitis (Wegener's) treated with rituximab.

OBJECTIVE Granulomatosis with polyangiitis (GPA), also known as Wegeners granulomatosis, is an autoimmune disease characterized by inflammation of blood vessels most often seen in the upper respiratory tract, lungs, kidneys, and skin. Central nervous system (CNS) involvement of GPA is rare, particularly in the pituitary, and can be difficult to treat. METHODS Case report. RESULTS We present a 30-year-old woman with pituitary and ocular GPA, whose unusually recalcitrant disease led to the development of pan-hypopituitarism and near-total vision loss. After failing multiple systemic immunosuppressants, she was ultimately treated with the novel immunomodulatory agent rituximab together with pulse corticosteroids, which achieved a gratifying response. CONCLUSION Pituitary and optic chiasm involvement is a rare complication of GPA. We believe this case illustrates the complexity of management of pituitary GPA and provides insight into the potential utility of the biologic agent rituximab in this disease.