Craniotomy: Any operation on the cranium or incision into the cranium. (Dorland, 28th ed)Neurosurgical Procedures: Surgery performed on the nervous system or its parts.Pneumocephalus: Presence of air or gas within the intracranial cavity (e.g., epidural space, subdural space, intracerebral, etc.) which may result from traumatic injuries, fistulous tract formation, erosions of the skull from NEOPLASMS or infection, NEUROSURGICAL PROCEDURES, and other conditions.Frontal Bone: The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the NASAL BONE and the CHEEK BONE on each side of the face.Hematoma, Subdural, Acute: Accumulation of blood in the SUBDURAL SPACE with acute onset of neurological symptoms. Symptoms may include loss of consciousness, severe HEADACHE, and deteriorating mental status.Trephining: The removal of a circular disk of the cranium.Head Injuries, Penetrating: Head injuries which feature compromise of the skull and dura mater. These may result from gunshot wounds (WOUNDS, GUNSHOT), stab wounds (WOUNDS, STAB), and other forms of trauma.Brain Neoplasms: Neoplasms of the intracranial components of the central nervous system, including the cerebral hemispheres, basal ganglia, hypothalamus, thalamus, brain stem, and cerebellum. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are subdivided into benign and malignant forms. In general, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain.Delayed Emergence from Anesthesia: Abnormally slow pace of regaining CONSCIOUSNESS after general anesthesia (ANESTHESIA, GENERAL) usually given during surgical procedures. This condition is characterized by persistent somnolence.Hematoma, Subdural: Accumulation of blood in the SUBDURAL SPACE between the DURA MATER and the arachnoidal layer of the MENINGES. This condition primarily occurs over the surface of a CEREBRAL HEMISPHERE, but may develop in the spinal canal (HEMATOMA, SUBDURAL, SPINAL). Subdural hematoma can be classified as the acute or the chronic form, with immediate or delayed symptom onset, respectively. Symptoms may include loss of consciousness, severe HEADACHE, and deteriorating mental status.Intracranial Aneurysm: Abnormal outpouching in the wall of intracranial blood vessels. Most common are the saccular (berry) aneurysms located at branch points in CIRCLE OF WILLIS at the base of the brain. Vessel rupture results in SUBARACHNOID HEMORRHAGE or INTRACRANIAL HEMORRHAGES. Giant aneurysms (>2.5 cm in diameter) may compress adjacent structures, including the OCULOMOTOR NERVE. (From Adams et al., Principles of Neurology, 6th ed, p841)Dura Mater: The outermost of the three MENINGES, a fibrous membrane of connective tissue that covers the brain and the spinal cord.Surgical Fixation Devices: Devices used to hold tissue structures together for repair, reconstruction or to close wounds. They may consist of adsorbable or non-adsorbable, natural or synthetic materials. They include tissue adhesives, skin tape, sutures, buttons, staples, clips, screws, etc., each designed to conform to various tissue geometries.Meningeal Neoplasms: Benign and malignant neoplastic processes that arise from or secondarily involve the meningeal coverings of the brain and spinal cord.Supratentorial Neoplasms: Primary and metastatic (secondary) tumors of the brain located above the tentorium cerebelli, a fold of dura mater separating the CEREBELLUM and BRAIN STEM from the cerebral hemispheres and DIENCEPHALON (i.e., THALAMUS and HYPOTHALAMUS and related structures). In adults, primary neoplasms tend to arise in the supratentorial compartment, whereas in children they occur more frequently in the infratentorial space. Clinical manifestations vary with the location of the lesion, but SEIZURES; APHASIA; HEMIANOPSIA; hemiparesis; and sensory deficits are relatively common features. Metastatic supratentorial neoplasms are frequently multiple at the time of presentation.Frontal Sinus: One of the paired, but seldom symmetrical, air spaces located between the inner and outer compact layers of the FRONTAL BONE in the forehead.Meningioma: A relatively common neoplasm of the CENTRAL NERVOUS SYSTEM that arises from arachnoidal cells. The majority are well differentiated vascular tumors which grow slowly and have a low potential to be invasive, although malignant subtypes occur. Meningiomas have a predilection to arise from the parasagittal region, cerebral convexity, sphenoidal ridge, olfactory groove, and SPINAL CANAL. (From DeVita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2056-7)Arachnoid Cysts: Intracranial or spinal cavities containing a cerebrospinal-like fluid, the wall of which is composed of arachnoidal cells. They are most often developmental or related to trauma. Intracranial arachnoid cysts usually occur adjacent to arachnoidal cistern and may present with HYDROCEPHALUS; HEADACHE; SEIZURES; and focal neurologic signs. (From Joynt, Clinical Neurology, 1994, Ch44, pp105-115)Subdural Space: Potential cavity which separates the ARACHNOID MATER from the DURA MATER.Microsurgery: The performance of surgical procedures with the aid of a microscope.Glasgow Coma Scale: A scale that assesses the response to stimuli in patients with craniocerebral injuries. The parameters are eye opening, motor response, and verbal response.Hematoma, Epidural, Cranial: Accumulation of blood in the EPIDURAL SPACE between the SKULL and the DURA MATER, often as a result of bleeding from the MENINGEAL ARTERIES associated with a temporal or parietal bone fracture. Epidural hematoma tends to expand rapidly, compressing the dura and underlying brain. Clinical features may include HEADACHE; VOMITING; HEMIPARESIS; and impaired mental function.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Hematoma, Subdural, Chronic: Accumulation of blood in the SUBDURAL SPACE with delayed onset of neurological symptoms. Symptoms may include loss of consciousness, severe HEADACHE, and deteriorating mental status.Cerebrospinal Fluid Rhinorrhea: Discharge of cerebrospinal fluid through the nose. Common etiologies include trauma, neoplasms, and prior surgery, although the condition may occur spontaneously. (Otolaryngol Head Neck Surg 1997 Apr;116(4):442-9)Temporal Bone: Either of a pair of compound bones forming the lateral (left and right) surfaces and base of the skull which contains the organs of hearing. It is a large bone formed by the fusion of parts: the squamous (the flattened anterior-superior part), the tympanic (the curved anterior-inferior part), the mastoid (the irregular posterior portion), and the petrous (the part at the base of the skull).Cranial Fossa, Anterior: The compartment containing the inferior part and anterior extremities of the frontal lobes (FRONTAL LOBE) of the cerebral hemispheres. It is formed mainly by orbital parts of the FRONTAL BONE and the lesser wings of the SPHENOID BONE.Fourth Ventricle: An irregularly shaped cavity in the RHOMBENCEPHALON, located between the MEDULLA OBLONGATA; the PONS; and the isthmus in front, and the CEREBELLUM behind. It is continuous with the central canal of the cord below and with the CEREBRAL AQUEDUCT above, and through its lateral and median apertures it communicates with the SUBARACHNOID SPACE.Stereotaxic Techniques: Techniques used mostly during brain surgery which use a system of three-dimensional coordinates to locate the site to be operated on.Brain Abscess: A circumscribed collection of purulent exudate in the brain, due to bacterial and other infections. The majority are caused by spread of infected material from a focus of suppuration elsewhere in the body, notably the PARANASAL SINUSES, middle ear (see EAR, MIDDLE); HEART (see also ENDOCARDITIS, BACTERIAL), and LUNG. Penetrating CRANIOCEREBRAL TRAUMA and NEUROSURGICAL PROCEDURES may also be associated with this condition. Clinical manifestations include HEADACHE; SEIZURES; focal neurologic deficits; and alterations of consciousness. (Adams et al., Principles of Neurology, 6th ed, pp712-6)Neurosurgery: A surgical specialty concerned with the treatment of diseases and disorders of the brain, spinal cord, and peripheral and sympathetic nervous system.Hematocele: Hemorrhage into a canal or cavity of the body, such as the space covered by the serous membrane (tunica vaginalis) around the TESTIS leading to testicular hematocele or scrotal hematocele.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Surgical Instruments: Hand-held tools or implements used by health professionals for the performance of surgical tasks.Postoperative Complications: Pathologic processes that affect patients after a surgical procedure. They may or may not be related to the disease for which the surgery was done, and they may or may not be direct results of the surgery.Cerebellar Diseases: Diseases that affect the structure or function of the cerebellum. Cardinal manifestations of cerebellar dysfunction include dysmetria, GAIT ATAXIA, and MUSCLE HYPOTONIA.Ventriculostomy: Surgical creation of an opening in a cerebral ventricle.Surgical Flaps: Tongues of skin and subcutaneous tissue, sometimes including muscle, cut away from the underlying parts but often still attached at one end. They retain their own microvasculature which is also transferred to the new site. They are often used in plastic surgery for filling a defect in a neighboring region.Skull Base: The inferior region of the skull consisting of an internal (cerebral), and an external (basilar) surface.Consciousness Monitors: Devices used to assess the level of consciousness especially during anesthesia. They measure brain activity level based on the EEG.Brain Injuries: Acute and chronic (see also BRAIN INJURIES, CHRONIC) injuries to the brain, including the cerebral hemispheres, CEREBELLUM, and BRAIN STEM. Clinical manifestations depend on the nature of injury. Diffuse trauma to the brain is frequently associated with DIFFUSE AXONAL INJURY or COMA, POST-TRAUMATIC. Localized injuries may be associated with NEUROBEHAVIORAL MANIFESTATIONS; HEMIPARESIS, or other focal neurologic deficits.Cranial Nerve Neoplasms: Benign and malignant neoplasms that arise from one or more of the twelve cranial nerves.Skull Fractures: Fractures of the skull which may result from penetrating or nonpenetrating head injuries or rarely BONE DISEASES (see also FRACTURES, SPONTANEOUS). Skull fractures may be classified by location (e.g., SKULL FRACTURE, BASILAR), radiographic appearance (e.g., linear), or based upon cranial integrity (e.g., SKULL FRACTURE, DEPRESSED).Cerebral Angiography: Radiography of the vascular system of the brain after injection of a contrast medium.Subarachnoid Hemorrhage: Bleeding into the intracranial or spinal SUBARACHNOID SPACE, most resulting from INTRACRANIAL ANEURYSM rupture. It can occur after traumatic injuries (SUBARACHNOID HEMORRHAGE, TRAUMATIC). Clinical features include HEADACHE; NAUSEA; VOMITING, nuchal rigidity, variable neurological deficits and reduced mental status.Aneurysm, Ruptured: The tearing or bursting of the weakened wall of the aneurysmal sac, usually heralded by sudden worsening pain. The great danger of a ruptured aneurysm is the large amount of blood spilling into the surrounding tissues and cavities, causing HEMORRHAGIC SHOCK.Skull Base Neoplasms: Neoplasms of the base of the skull specifically, differentiated from neoplasms of unspecified sites or bones of the skull (SKULL NEOPLASMS).Conscious Sedation: A drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway. (From: American Society of Anesthesiologists Practice Guidelines)Cerebral Veins: Veins draining the cerebrum.Intracranial Hemorrhages: Bleeding within the SKULL, including hemorrhages in the brain and the three membranes of MENINGES. The escape of blood often leads to the formation of HEMATOMA in the cranial epidural, subdural, and subarachnoid spaces.Decompression, Surgical: A surgical operation for the relief of pressure in a body compartment or on a body part. (From Dorland, 28th ed)Craniopharyngioma: A benign pituitary-region neoplasm that originates from Rathke's pouch. The two major histologic and clinical subtypes are adamantinous (or classical) craniopharyngioma and papillary craniopharyngioma. The adamantinous form presents in children and adolescents as an expanding cystic lesion in the pituitary region. The cystic cavity is filled with a black viscous substance and histologically the tumor is composed of adamantinomatous epithelium and areas of calcification and necrosis. Papillary craniopharyngiomas occur in adults, and histologically feature a squamous epithelium with papillations. (From Joynt, Clinical Neurology, 1998, Ch14, p50)Brain Diseases: Pathologic conditions affecting the BRAIN, which is composed of the intracranial components of the CENTRAL NERVOUS SYSTEM. This includes (but is not limited to) the CEREBRAL CORTEX; intracranial white matter; BASAL GANGLIA; THALAMUS; HYPOTHALAMUS; BRAIN STEM; and CEREBELLUM.Anterior Cerebral Artery: Artery formed by the bifurcation of the internal carotid artery (CAROTID ARTERY, INTERNAL). Branches of the anterior cerebral artery supply the CAUDATE NUCLEUS; INTERNAL CAPSULE; PUTAMEN; SEPTAL NUCLEI; GYRUS CINGULI; and surfaces of the FRONTAL LOBE and PARIETAL LOBE.Orbit: Bony cavity that holds the eyeball and its associated tissues and appendages.Cranial Fossa, Middle: The compartment containing the anterior extremities and half the inferior surface of the temporal lobes (TEMPORAL LOBE) of the cerebral hemispheres. Lying posterior and inferior to the anterior cranial fossa (CRANIAL FOSSA, ANTERIOR), it is formed by part of the TEMPORAL BONE and SPHENOID BONE. It is separated from the posterior cranial fossa (CRANIAL FOSSA, POSTERIOR) by crests formed by the superior borders of the petrous parts of the temporal bones.Neuroendoscopy: PROCEDURES that use NEUROENDOSCOPES for disease diagnosis and treatment. Neuroendoscopy, generally an integration of the neuroendoscope with a computer-assisted NEURONAVIGATION system, provides guidance in NEUROSURGICAL PROCEDURES.Intracranial Hemorrhage, Hypertensive: Bleeding within the SKULL that is caused by systemic HYPERTENSION, usually in association with INTRACRANIAL ARTERIOSCLEROSIS. Hypertensive hemorrhages are most frequent in the BASAL GANGLIA; CEREBELLUM; PONS; and THALAMUS; but may also involve the CEREBRAL CORTEX, subcortical white matter, and other brain structures.Skull: The SKELETON of the HEAD including the FACIAL BONES and the bones enclosing the BRAIN.Monitoring, Intraoperative: The constant checking on the state or condition of a patient during the course of a surgical operation (e.g., checking of vital signs).