Neurosurgical Preoperative and Diagnostic Review

Vocabulary-style flashcards covering neurosurgical incidences, preoperative evaluations, complications, and diagnostic imaging characteristics based on lecture notes.

Wrong-side surgery incidence (craniotomies)

$2.2$ per $10,000$ craniotomies.

General wrong-site/wrong-patient incidence

Roughly $1$ in every $100,000$ operations.

Retained instruments and sponges frequency

$1$ in every $5,500$ to $10,000$ operations.

Orthopedic surgery

The medical specialty most likely to perform wrong-site or wrong-level surgery.

Surgical site infections (SSIs) rate (neurosurgical)

Approximately $0.01$ of neurosurgical cases.

Spine cases

The group with a higher frequency of surgical site infections compared to cranial cases.

Preanesthetic evaluation aim

To minimize overall patient morbidity associated with surgery and anesthesia.

Chronic anticonvulsant therapy effect

Increases resistance and requirement for nondepolarizing muscle relaxants.

Succinylcholine adverse effect (motor deficits)

Can lead to life-threatening Hyperkalemia in patients with major preexisting motor deficits.

Frailty

A decrement in physiologic reserves that affects a patient's resilience to recover from illness or stress.

Smoking cessation (mucociliary clearance)

Requires a period of $6$ to $8$ weeks.

Smoking cessation (24 hours)

Reduces carboxyhemoglobin levels and improves oxygenation.

Myocardial infarction surgical delay

$\ge 60$ days should elapse before performing a noncardiac surgical procedure.

Mannitol

An osmotic diuretic that must be used judiciously or avoided in patients with left ventricular failure and is contraindicated in anuria.

Balloon angioplasty delay

$14$ days recommended delay for elective noncardiac operations.

Bare metal stent delay

$30$ days delay for elective noncardiac operations.

Drug-eluting stent delay

$365$ days delay for elective noncardiac operations.

Sulfonylureas and metformin

Diabetic medications that should be withheld $24$ to $48$ hours before surgery.

Cushing syndrome (neurosurgical source)

Most commonly caused by exogenous administration of steroid hormones.

Cushing syndrome imbalance

Hypokalemic metabolic alkalosis.

Preoperative NSAID discontinuation

Aspirin should typically be discontinued one week before surgery.

Factor $Xa$ inhibitors preoperative withholding

At least $48$ hours.

Preoperative hyperglycemia concern

Can worsen neurological outcomes following episodes of Cerebral ischemia.

Levetiracetam (Keppra)

Often the first choice for prophylactic anticonvulsant use due to a lack of side effects and fewer drug interactions.

Acromegaly (radial artery cannulation)

Hazardous because hypertrophic ligaments can cause carpal tunnel syndrome, compromising ulnar flow.

Brain swelling predictors (intracranial tumors)

Midline shift, peritumoral edema, and a diagnosis of glioblastoma multiforme or metastasis.

Carotid endarterectomy (CEA) morbidity

Cardiac complications are the most common cause of postoperative medical morbidity and fatality.

Fisher scale

Grading for subarachnoid hemorrhage based on the amount of subarachnoid blood seen on a CT scan.

Cerebral salt wasting syndrome

A condition in SAH involves hyponatremia associated with hypovolemia; requires saline treatment.

SIADH treatment vs. Cerebral salt wasting

SIADH requires fluid restriction, while cerebral salt wasting requires fluids (saline).

Spetzler-Martin scale

Grading system used to estimate surgical risk for arteriovenous malformation (AVM) resection.

Probe-patent foramen ovale (PFO)

A relative contraindication to the sitting position due to risk of paradoxical air embolism from right-to-left pressure gradient reversal.

Venous air embolism

The most common complication associated with the sitting position.

nTMS lower extremity mapping

Requires $10\%$ to $20\%$ higher intensity than mapping small hand muscles.

nTMS focality

Induced current flow must be Perpendicular to the nearest sulcus.

EMG quality threshold (nTMS)

Resting activity should be below $50\, \mu V$.

nTMS language mapping frequency

$4$ to $10\, Hz$.

nTMS artifact resistance

Considered less susceptible than fMRI because it is not affected by changes in oxygenation.

nTMS magnetic field limitation

Cannot reach deep brain structures like the temporomesial or frontobasal gyri.

Routine brain CT scan

Consists of $5\text{-mm}$ contiguous axial images from the skull base to the vertex.

Acute epidural hematoma shape

Biconvex (lens-shaped).

Subdural hematoma (SDH) border shape

Concave border approximating the contour of the cerebral hemisphere.

Interhemispheric fissure

The midline dural reflections that limit the spread of a subdural hematoma.

Nontraumatic SAH (primary cause)

Rupture of an intracranial aneurysm.

Microscopic tumor infiltration imaging

MRI (specifically T2-weighted and FLAIR) is superior for evaluating infiltration and defining borders.

Choline peak (MRS)

Elevation suggests a recurrent neoplasm over radiation necrosis.

Oligodendrogliomas calcification

Occurs histologically in $0.7$ ($70\%$) of cases.

Meningioma

The most common nonglial primary brain neoplasm; characterized by the 'dural tail' sign on MRI.

Pituitary macroadenoma threshold

Greater than $1\, cm$ in size.

Brain metastasis localization

Typically at the gray matter—white matter junction.

Vestibular schwannoma

The most common mass lesion found in the cerebellopontine angle.

Diffusion-weighted imaging (DWI)

Identify acute brain infarctions within $30$ minutes to $1$ hour.

T2 shine-through effect

An imaging sign on DWI that appears after the hyperintense period of an acute infarction has passed.

Gradient-recalled echo (GRE)

Highly sensitive to susceptibility changes caused by acute blood breakdown products in trauma.

Cavernous malformations MRI appearance

Classic 'popcorn' appearance with heterogeneous hypointensity and hyperintensity.

Developmental Venous Anomaly (DVA)

Often described as resembling the head of Medusa on imaging.

Mesial temporal sclerosis

Associated with hippocampal atrophy and abnormal hyperintensity on T2-weighted images.

Bone marrow change detection (radiographs)

A change of $30\%$ to $75\%$ must occur to be apparent on spine radiographs.

Myelographic block

A condition where contrast material fails to extend cranially during myelography due to mass effect.

Short tau inversion recovery (STIR)

The most sensitive MRI sequence for identifying bone marrow involvement in the spine.

CSF flow (systole)

Demonstrated as Hyperintense during caudal flow.

Modic Type I changes

Decreased signal on T1 and increased signal on T2, representing edema.

Modic Type II changes

Fatty marrow replacement (increased signal on T1, isointense/hyperintense on T2).

Modic Type III changes

Representing sclerosis with low signal intensity on all pulse sequences.

Broad-based disc herniation

Involves between $0.25$ ($25\%$) and $0.5$ ($50\%$) of the disc circumference.

Disc extrusion

A herniation where the distance between the edges of the material is greater than the base distance.

Sequestration

Disc material that has lost all continuity with the parent disc.

Degenerative spondylolisthesis site

Most commonly at the $L4—L5$ level.

Schmorl nodes

Intravertebral herniations through a defect in the vertebral body end plate.

Vertebral osteomyelitis MRI

Confluent decreased T1 signal of the disc and adjacent bodies, and increased T2 signal within the disc space.

Epidural abscess vs. Phlegmon

An abscess shows peripheral enhancement (ring-enhancing), while a phlegmon enhances homogeneously.

Postoperative scar vs. Disc herniation

Scar tissue (epidural fibrosis) enhances homogeneously and immediately; discs enhance only peripherally or on delayed images.

Group I arachnoiditis

Defining imaging feature is clumping of individual traversing nerve roots within the thecal sac.

Group II arachnoiditis

Characterized by a 'featureless' thecal sac where individual nerve roots cannot be identified.

Open spinal dysraphism

Defective midline closure exposed to the environment (e.g., myelomeningocele).

Diastematomyelia

A sagittal division of the spinal cord into two hemicords.

Type II vascular malformation

An intramedullary glomus AVM.

Postoperative neurocognitive disorders

Most significant as complications for geriatric patients.

Unilateral cortical lesions

Generally do not result in coma unless brainstem herniation occurs.

Midcervical flexion myelopathy (quadriplegia)

A risk associated with the sitting position during posterior fossa surgery.