Paul E. Kim

The trigeminal nerve.

The trigeminal nerve is the largest of the cranial nerves, serving as a major conduit for sensory information from the head and neck and primarily providing motor innervation to the muscles of mastication. An understanding of the pathologic processes that may involve this nerve requires a detailed knowledge of its origin within the brain stem as well as its course intracranially. This article describes the neuroanatomy of the nerve and divides it into its various segments to provide a differential diagnosis of common and some uncommon pathologic processes.

Clinical Applications of Diffusion Tensor Imaging

Advancements in diffusion-weighted imaging during the past decade have led to the use of diffusion tensor imaging to further characterize the structural integrity of neural tissue and to noninvasively trace neuronal tracts in the brain and spine. This has led to many clinical applications that have aided in surgical planning for brain and spinal cord tumors and has increased the diagnostic potential of magnetic resonance imaging in disorders such as multiple sclerosis, Alzheimer disease, and traumatic brain injury.

Stereotactic radiosurgery: adjacent tissue injury and response after high-dose single fraction radiation: Part I--Histology, imaging, and molecular events.

RADIOSURGERY IS NOW the preferred treatment modality for many intracranial disease processes. Although almost 50 years have passed since it was introduced as a tool to treat neurological disease, investigations into its effects on normal tissues of the central nervous system are still ongoing. The need for these continuing studies must be underscored. A fundamental understanding of the brain parenchymal response to radiosurgery would permit development of strategies that would enhance and potentiate the radiosurgical treatment effects on diseased tissue while mitigating injury to normal structures. To date, most studies on the response of the central nervous system to radiosurgery have been performed on brain tissue in the absence of pathological lesions, such as benign tumors or metastases. Although instructive, these investigations fail to emulate the majority of clinical scenarios that involve radiosurgical treatment of specific lesions surrounded by normal brain parenchyma. This article is the first in a two-part series that addresses the brain parenchymas response to radiosurgery. This first article analyzes the histological, radiographic, and molecular data gathered regarding the brain parenchymal response to radiosurgery and aims to suggest future studies that could enhance our understanding of the topic. The second article in the series begins by discussing strategies for radiosurgical therapeutic enhancement. It concludes by focusing on strategies for mitigation and repair of radiation-induced brain injury.

Reliability of three-dimensional fluoroscopy for detecting pedicle screw violations in the thoracic and lumbar spine.

OBJECTIVE:Thoracic and lumbar pedicle screws have become popular because of their biomechanical superiority over other methods of spinal fixation. However, the safety and efficacy of transpedicular screws depend on their proper placement. Recent advances in imaging have resulted in the ability to acquire three-dimensional (3-D) axial images of the spine during surgery, and this study was undertaken to assess the reliability of this technology to detect pedicle violations. METHODS:Pedicle screws were placed in six human cadaver spines from T1 to S1 using standard techniques. Intentional pedicle violations were created in 74 of 216 pedicles, and violations were graded on a four-point scale (range, 0–3). Radiographic images were then obtained using a conventional spiral computed tomographic scanner and the Siremobil Iso-C 3D (Siemens Medical Solutions, Erlangen, Germany) 3-D fluoroscopy unit. An independent neuroradiologist then graded pedicle violations as ascertained by the two imaging modalities. RESULTS:Using direct inspection of the pedicles as the “gold standard,” the overall sensitivity and specificity for detecting pedicle violations were 0.716 and 0.789, respectively, with 3-D fluoroscopy. The overall sensitivity and specificity for detecting pedicle violations were 0.608 and 0.937, respectively, with conventional computed tomography. All Grade 2 pedicle violations were detected in the thoracic spine by both modalities, and all Grade 3 violations were detected by both modalities. CONCLUSION:Axial images obtained with 3-D fluoroscopy demonstrate a higher sensitivity but lower specificity than conventional computed tomographic scanning for assessing pedicle violations. By providing real-time intraoperative imaging, 3-D fluoroscopy may enhance the safety of thoracic transpedicular instrumentation.

Imaging of the pituitary and parasellar region

The pituitary is part of a chain of enormous biologic amplification, which is regulated by a small amount of releasing factors in the portal blood from the hypothalamus. The pituitary is a master gland that regulates a number of hormones. A subtle abnormality in the pituitary can cause significant changes in body metabolism. Because the pituitary glands are small structures, high-resolution imaging techniques are required to satisfactorily evaluate the gland. It is imperative for the radiologist to be familiar with the anatomy, physiology, and pathology of the pituitary gland, which provides a solid foundation for accurate interpretation of the imaging studies of the pituitary gland.

Visualizing the Future: Enhancing Neuroimaging with Nanotechnology

Advancements in imaging of the central nervous system have paralleled and propelled neurosurgical practice. These technologic innovations have expanded our understanding of neuroanatomy and neuropathology, helping to refine neurosurgical techniques to be more precise and less invasive. Nanotechnology will play a significant role in the next wave of technology that will continue to improve neurosurgical practice. With specific regard to neuroimaging, nanotechnology has the potential to provide more precise resolution when imaging nervous system malignancies. Nanoparticles may be engineered to noninvasively visualize pathology once found only under a microscope. They will enhance our ability to target new disease processes and thus develop more precise surgical and nonsurgical treatments. This article will discuss the background of nanotechnologys use in imaging of the nervous system, its current status, and future potentials.

Perfusion and permeability MR imaging of gliomas.

Conventional contrast-enhanced MR imaging is the current standard technique for the diagnosis and treatment evaluation of gliomas and other brain neoplasms. However, this method is quite limited in its ability to characterize the complex biology of gliomas and so there is a need to develop more quantitative imaging methods. Perfusion and permeability MR imaging are two such techniques that have shown promise in this regard. This review will highlight the underlying principles, applications, and pitfalls of these evolving advanced MRI methods.

Radiographic assessment of cranial gunshot wounds.

Though advances in MRI will undoubtedly increase its use, particularly in the subacute period, CT will likely continue its primary role in the management of these injuries in the foreseeable future. The spectrum of imaging features of cranial gunshot injuries is vast, because they encompass all of the findings encountered in closed head injury in addition to the wide variety of problems associated with penetration. Thus, only a brief summary of the many varied aspects of this complex problem is presented here as a review of the more salient issues.

Diffusion tensor imaging in the assessment of ossification of the posterior longitudinal ligament: a report on preliminary results in 3 cases and review of the literature

Cervical spondylotic myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is a common neurosurgical disease that carries high morbidity. OPLL and other degenerative processes cause narrowing of the central canal, with subsequent spinal cord injury. Repeated minor trauma and vascular aberrations have been purported to underlie cervical spondylotic myelopathy, although the exact pathophysiological mechanism is unclear. Regardless, detection of early axonal damage may allow more timely surgical intervention and prediction of functional outcome. Diffusion tensor (DT) imaging of the cervical spine is a novel technique with improved sensitivity compared with conventional anatomical MR imaging that is currently available on most clinical scanners. This review describes the theoretical basis, application, and analysis of DT imaging as it pertains to neurosurgery. Particular emphasis is placed on OPLL.

From Atom to Brain: Applications of Molecular Imaging to Neurosurgery

Molecular imaging is a field born out of the happy marriage of molecular biology and radiology. The first installment of this two-part series on molecular imaging demonstrated basic principles for practitioners in the field of the neurosciences. This installment seeks to provide some illustrative examples, insights, and specific applications to the neurosciences. The fields of functional neurosurgery including the treatment of neuropsychiatric disorders, novel treatments and imaging of tumors, neuroregenerative medicine, and nanotechnology in vascular disorders are covered. Finally, we give some parting thoughts on the future of molecular imaging, including advances in the imaging of neurodegenerative disorders.