ABNS Neurological Surgery key terms

The principle that the skull is a rigid container holding brain, blood, and CSF at a nearly fixed total volume, so any increase in one component must be offset by a decrease in another or intracranial pressure rises.

The driving pressure for brain blood flow, calculated as mean arterial pressure minus intracranial pressure; it is the target manipulated in neurocritical care to prevent ischemic secondary injury.

The pulsatile pressure tracing within the skull, normally showing three peaks per cardiac cycle; loss of the second peak or appearance of plateau waves signals falling intracranial compliance.

Surgical removal of a large skull vault flap to allow a swollen hemisphere to expand outward, used for refractory intracranial hypertension such as malignant middle cerebral artery infarction or severe traumatic brain injury.

Severe progressive brain swelling after large hemispheric infarction that causes mass effect, midline shift, and herniation, typically peaking days after onset and often requiring decompressive surgery.

Patterns of brain displacement across dural or bony boundaries, such as subfalcine, transtentorial, and tonsillar herniation, each producing characteristic clinical deterioration from compression of adjacent structures.

The triad of hypertension, bradycardia, and irregular respiration that appears with severe raised intracranial pressure, reflecting brainstem compression and impending herniation.

Traumatic shearing of white matter tracts from rotational acceleration-deceleration forces, producing punctate hemorrhages at gray-white junctions and often prolonged coma without a large mass lesion.

Blood accumulating between skull and dura, usually from middle meningeal artery tearing with a temporal bone fracture, classically causing a lucid interval followed by rapid deterioration.

Blood collecting between dura and arachnoid, typically from tearing of bridging cortical veins, often associated with more severe underlying brain injury than epidural collections.

An encapsulated collection of degraded blood products over the hemisphere that evolves over weeks, common in older or anticoagulated patients, and often treated with burr-hole drainage.

Bleeding into the subarachnoid space from rupture of an intracranial aneurysm, presenting with sudden severe headache and carrying risks of rebleeding, vasospasm, and hydrocephalus.

Neurological deterioration from reduced cerebral blood flow days after subarachnoid hemorrhage, driven by vasospasm and other processes, and a major cause of poor outcome.

A dihydropyridine calcium channel blocker given orally or enterally after subarachnoid hemorrhage; it improves neurological outcome without clearly reversing large-vessel vasospasm.

Noninvasive ultrasound through skull windows that measures flow velocities in major cerebral arteries, used to screen for vasospasm and to assess cerebrovascular reactivity.

A tangle of abnormal arteries and veins without an intervening capillary bed, creating high-flow shunts that can rupture, cause seizures, or steal blood from normal brain.

A surgical risk score for brain arteriovenous malformations combining nidus size, eloquence of adjacent brain, and presence of deep venous drainage into a five-point scale.

Catheter-based X-ray imaging that subtracts bone before contrast injection, giving the highest-resolution view of cerebral arteries and veins and remaining the reference standard for vascular lesions.

Progressive narrowing of the distal internal carotid and proximal cerebral arteries with compensatory fragile collateral vessels, causing stroke in children and hemorrhage in adults, treated with revascularization.

The most common malignant primary brain tumor in adults, an infiltrative astrocytic neoplasm with necrosis and microvascular proliferation that recurs despite surgery, radiation, and chemotherapy.

Epigenetic silencing of the DNA repair gene MGMT in glioma cells, which predicts greater benefit from alkylating chemotherapy such as temozolomide.

The proportion of a tumor removed at surgery, assessed on postoperative imaging; greater removal of enhancing tumor is associated with longer survival in high-grade glioma.

New contrast enhancement or edema on imaging shortly after chemoradiation that mimics tumor growth but reflects treatment-related inflammation and often resolves without change in therapy.

A usually benign tumor arising from arachnoid cap cells, typically extra-axial and dural-based, often curable by complete resection including its dural attachment.

A five-tier classification of the extent of meningioma removal and its dural and bony attachments, correlating with the likelihood of tumor recurrence.

A neoplasm of the anterior pituitary that may secrete hormones or cause mass effect on the optic chiasm, frequently approached through the sphenoid sinus.

A minimally invasive corridor to the skull base and pituitary through the nasal cavity and sphenoid sinus, avoiding brain retraction but requiring careful repair of dural defects.

Escape of CSF through a dural and bony defect, presenting as clear rhinorrhea or otorrhea, which risks ascending infection and often needs surgical repair.

A benign tumor of Schwann cells on the vestibular division of the eighth cranial nerve, causing progressive unilateral hearing loss, tinnitus, and eventually brainstem compression.

Intraoperative electrical stimulation and recording of facial muscles used during cerebellopontine angle and skull base surgery to identify and preserve the facial nerve.

Abnormal accumulation of cerebrospinal fluid causing ventricular enlargement and raised pressure, resulting from obstruction, impaired absorption, or overproduction.

A syndrome of enlarged ventricles with normal measured CSF pressure, causing gait disturbance, urinary incontinence, and cognitive decline that may improve after shunt placement.

Creation of a stoma in the floor of the third ventricle to let CSF bypass an obstruction, an alternative to shunting in selected cases of obstructive hydrocephalus.

Downward displacement of the cerebellar tonsils through the foramen magnum, which can obstruct CSF flow and cause headache, syringomyelia, or brainstem symptoms.

A fluid-filled cavity within the spinal cord that expands over time and produces a cape-like loss of pain and temperature sensation, often associated with Chiari malformation or trauma.

The intrinsic ability of cerebral vessels to dilate or constrict to keep blood flow relatively constant across a range of blood pressures, which can be impaired after injury.

Hypoperfused but still viable brain tissue surrounding an infarct core that can be salvaged if blood flow is restored promptly.

Selective intracarotid injection of a short-acting anesthetic to determine hemispheric dominance for language and memory before epilepsy surgery.

The cortical region where epileptic discharges begin, identified by scalp or intracranial recordings and targeted for resection in drug-resistant epilepsy.

Craniotomy performed with the patient conscious during mapping so that cortical and subcortical regions serving speech and movement can be identified and spared during resection.

Implantation of electrodes in deep brain targets connected to a programmable generator, used to modulate pathological circuits in movement disorders and other conditions.

A rigid head-fixed coordinate system that lets instruments reach a precise intracranial point using imaging-defined three-dimensional coordinates.

Protrusion of nucleus pulposus through the annulus that compresses a nerve root, typically causing radiculopathy in a specific dermatomal pattern.

Compression of the lumbosacral nerve roots below the conus medullaris, producing saddle anesthesia, bladder and bowel dysfunction, and leg weakness that demands urgent decompression.

Progressive spinal cord compression from degenerative disc and bone changes in the neck, causing gait disturbance, hand clumsiness, and hyperreflexia.

Compression of the median nerve at the wrist producing numbness and tingling in the thumb, index, and middle fingers, often worse at night.

A focal ballooning of an intracranial artery wall, most often at branch points of the circle of Willis, which may rupture to cause subarachnoid hemorrhage.

Structural or functional brain damage from external mechanical force, graded by the Glasgow Coma Scale and managed to prevent secondary injury from hypoxia, hypotension, and raised pressure.

A 3-to-15 point bedside score summing eye opening, verbal response, and motor response, used to grade consciousness and severity of brain injury.

Rapid and often fatal brain swelling that can occur when a second head injury is sustained before symptoms from a prior concussion have resolved.

Electrical responses recorded over the scalp after peripheral nerve stimulation, used to monitor the integrity of sensory pathways during spine and brain surgery.