Neuroinfections and Brain Tumors: Meningitis, Encephalitis, Gliomas, and More

Acute inflammation of the pia mater and arachnoid; may be bacterial or viral; bacterial pyogenic form is most common.

Meningitis

Infection reaches the meninges from the middle ear, upper respiratory tract, frontal sinus, bloodstream, lungs, or another infection site.

Meningitis

Subarachnoid enhancement in the basal cisterns and sylvian fissure may be seen on MRI.

Meningitis

Viral inflammation of the brain; if the meninges are also involved, it is called meningoencephalitis.

Encephalitis

Ranges from mild headache and fever to severe cerebral dysfunction, seizures, coma, hemorrhage, and death; herpes simplex is a common cause.

Encephalitis

Herpes infection producing a high-signal temporal-lobe lesion with possible midline shift on T2-weighted MRI.

Herpes simplex encephalitis

Usually results from chronic infection of the middle ear, paranasal sinuses, or mastoid air cells, or from systemic infection such as pneumonia, bacterial endocarditis, or osteomyelitis.

Brain abscess

Necrotic mass with a capsule and surrounding edema on MRI; CT may show thin, uniform rings of enhancement.

Brain abscess

Suppurative collection between the inner dura and outer arachnoid; most commonly spreads from the frontal or ethmoid sinuses.

Subdural empyema

May follow mastoiditis, middle-ear infection, purulent meningitis, penetrating skull wounds, craniectomy, or skull osteomyelitis.

Subdural empyema

Contrast CT shows a narrow enhancing zone separating an extracerebral collection from the brain surface.

Subdural empyema

Infection outside the dura but beneath the inner table of the skull; almost always associated with cranial osteomyelitis.

Epidural empyema

Usually begins in the ear or paranasal sinuses and commonly affects the frontal region because of its proximity to the frontal sinuses.

Epidural empyema

MRI may show a black rim of dura outlining an epidural fluid collection.

Epidural empyema

Usually caused by direct extension of a suppurative process from the paranasal sinuses, mastoid air cells, or scalp.

Osteomyelitis of the skull

Radiographic changes develop 1-2 weeks after clinical onset and may show diffuse osteolytic destruction.

Osteomyelitis of the skull

Most common primary malignant brain tumor; composed of glial cells and spreads by direct extension.

Glioma

May cross from one cerebral hemisphere to the other through white-matter tracts such as the corpus callosum; peak incidence is middle age and MRI is preferred.

Glioma

Highly aggressive glioma that is predominantly cerebral.

Glioblastoma

Most common glioma, about 70%; slow-growing and infiltrative and may form large cavities or pseudocysts.

Astrocytoma

Glioma arising most often from the fourth-ventricle walls in children and the lateral ventricles in adults.

Ependymoma

Rapidly growing tumor that spreads through cerebrospinal fluid.

Medulloblastoma

Slow-growing cerebral glioma that tends to calcify.

Oligodendrocytoma

Benign tumor arising from arachnoid lining cells and attached to the dura mater.

Meningioma

Commonly occurs along the calvarial convexity, olfactory groove, tuberculum sellae, parasagittal region, sylvian fissure, cerebellopontine angle, or spinal canal.

Meningioma

Slow-growing benign tumor arising from Schwann cells in the vestibular portion of cranial nerve VIII.

Acoustic neuroma

Usually begins in the internal auditory canal and extends into the cerebellopontine angle cistern; may be solitary or associated with neurofibromatosis.

Acoustic neuroma

Usually arises in the anterior pituitary; the most common type is a nonsecreting chromophobe tumor whose mass effect suppresses pituitary secretion.

Pituitary adenoma

Hormone-secreting form causes symptoms of hormone excess, including gigantism in adolescents and acromegaly in adults.

Pituitary adenoma

Mass arises from the sella turcica and may extend upward into the suprasellar cistern on MRI.

Pituitary adenoma

Benign tumor with cystic and solid components, usually occurring before age 20 and located above the sella turcica.

Craniopharyngioma

Suprasellar tumor that depresses the optic chiasm and may extend into the third ventricle.

Craniopharyngioma

Germinoma and teratoma are rapidly growing germ-cell tumors most common in males younger than 25.

Pineal tumors

Tumor arising from notochord remnants; most common at the clivus and lumbosacral region.

Chordoma

Locally invasive but does not metastasize; may calcify and destroy the clivus, dorsum sellae, or petrous bone.

Chordoma

Multiple brain masses reached by hematogenous spread; lung and breast are the most common primary cancers.

Brain metastases

Multiple enhancing masses of varied size with extensive surrounding edema on CT or MRI.

Brain metastases

Its presence or absence does not predict intracranial injury; emergency CT, not plain skull radiography, is the modality of choice in head trauma.

Skull fracture

Sharp lucent line that is often irregular or jagged and may branch.

Linear skull fracture

Linear fracture that intersects a suture and travels along it, producing sutural separation.

Diastatic skull fracture

Often stellate with fracture lines radiating from a central point; overlapping fragments appear dense en face, and tangential views determine the depression.

Depressed skull fracture

Acute arterial cranial bleed, usually from laceration of the middle meningeal artery.

Epidural hematoma

Rapidly produces mass effect and acute neurologic symptoms; CT shows a peripheral biconvex or lens-shaped high-density lesion.

Epidural hematoma

Lens-shaped collection causing midline shift after trauma.

Epidural hematoma

Venous bleed, usually from a vein between the dura and the other meninges.

Subdural hematoma

Crescent-shaped peripheral high-density collection that follows the brain surface adjacent to the inner skull table.

Subdural hematoma

Brain-tissue injury caused by movement of the brain against rough skull surfaces after blunt trauma.

Cerebral contusion

CT shows low-density edema and tissue necrosis, sometimes with mixed-density punctate hemorrhages.

Cerebral contusion

Traumatic hemorrhage into the brain parenchyma caused by shearing of intraparenchymal arteries, usually at the gray-white matter junction.

Intracerebral hematoma

CT shows a well-circumscribed, homogeneous high-density region often surrounded by low-density edema.

Intracerebral hematoma

Traumatic hemorrhage that tends to occur opposite the site of direct impact; CT shows increased density in the basilar cisterns, fissures, and sulci.

Subarachnoid hemorrhage

Aneurysm rupture is its most common nontraumatic cause; MRI requires a fluid-attenuated inversion recovery sequence to demonstrate it.

Subarachnoid hemorrhage

Penetrating neck trauma such as gunshot or stabbing damages the extracerebral carotid arteries.

Carotid artery injury

Abnormal connection between the internal carotid artery and venous system, often the cavernous sinus, after a basal skull fracture or penetrating head trauma.

Traumatic carotid fistula

Most commonly fractured facial bones; image upright for air-fluid levels or use dorsal decubitus if upright imaging is impossible.

Nasal bone fracture

Direct frontal orbital blow sharply raises intraorbital pressure and fractures the thin, weak orbital floor.

Blowout fracture

Orbital-floor fragments and soft tissue may displace into the maxillary sinus; inferior rectus displacement may limit upward gaze.

Blowout fracture

Fractures of the zygomatic arch and orbital floor or rim with separation of the zygomaticofrontal suture.

Tripod fracture

Severe bilateral horizontal maxillary fractures form a large, unstable detached facial fragment; classified as types I, II, or III.

Le Fort fracture

Side blow produces inward displacement of the central arch fragments and outward displacement at the zygomatic and temporal ends; the submentovertex view is useful.

Zygomatic arch fracture

Common injury of the prominent lower facial skeleton; bilateral fractures are common.

Mandibular fracture

Sudden development of a focal neurologic deficit, also termed acute brain infarction; internal carotid arteries are most commonly involved.

Stroke

Disruption of cerebral blood flow caused by an obstruction.

Ischemic stroke

Disruption of cerebral blood flow caused by bleeding.

Hemorrhagic stroke

Chronic infarct appears as a sharply defined low-attenuation region on CT and may produce midline shift.

Middle cerebral artery infarct

Acute high-attenuation bleed surrounded by low-attenuation edema and producing midline shift.

Hemorrhagic stroke

Focal neurologic deficit that resolves completely within 24 hours.

Transient ischemic attack

Caused by emboli from an ulcerated arteriosclerotic plaque or stenosis of an extracerebral artery.

Transient ischemic attack

Precedes almost two-thirds of strokes; five-year cumulative stroke risk may be as high as 50%.

Transient ischemic attack

Most common surgically treatable source is disease at the carotid bifurcation; color-flow Doppler ultrasound is typically the initial examination.

Transient ischemic attack

Hemorrhagic stroke in which blood is contained within the functional brain tissue or brainstem.

Intraparenchymal hemorrhage

May result from head trauma, hypertensive vascular disease, congenital berry-aneurysm rupture, or arteriovenous malformation.

Intraparenchymal hemorrhage

Hypertensive form produces an oval or circular collection that displaces surrounding brain and may cause major mass effect.

Intraparenchymal hemorrhage

Noncontrast CT shows a homogeneous high-attenuation hematoma with adjacent low-attenuation ischemia and edema.

Intraparenchymal hemorrhage

Extension into the ventricular system is a very poor prognostic sign and may obstruct the third ventricle or foramen of Monro, enlarging the lateral ventricles.

Intraparenchymal hemorrhage

Major nontraumatic cause is rupture of a congenital berry aneurysm.

Subarachnoid hemorrhage

Most common cause of nontraumatic intraparenchymal hemorrhage in patients younger than 20; imaging shows a tangled vascular nidus with feeding arteries and draining veins.

Arteriovenous malformation

Most common demyelinating disorder; recurrent focal neurologic deficits with relapses and remissions.

Multiple sclerosis

Demyelination causes double vision, nystagmus, poor balance and coordination, tremor, weakness, dysarthria, and bladder dysfunction.

Multiple sclerosis

Primarily affects the spinal cord, optic nerves, and central white matter; peak incidence is 20-40 years with a strong female predominance.

Multiple sclerosis

MRI is preferred and shows scattered T2-bright demyelinating plaques; old inactive disease is low attenuation in deep and periventricular white matter on CT.

Multiple sclerosis

Temporary disturbance of brain impulses ranging from seconds of unconsciousness to violent generalized seizures; most cases are idiopathic, but head injury, birth trauma, or infection may cause it.

Epilepsy

Mildest form, most common in children; brief loss of consciousness with possible mild twitching and usually disappears in young adulthood.

Petit mal epilepsy

Generalized convulsions with falling, hypersalivation, and loss of bladder and sometimes bowel control.

Grand mal epilepsy

Calcified hippocampus indicating hippocampal sclerosis may be an imaging clue to this condition.

Seizure disorder

Imaging shows enlarged ventricles and prominent sulci caused by gradual neuronal loss.

Normal aging

Presenile dementia caused by diffuse progressive cerebral atrophy developing before the senile period.

Alzheimer disease

CT and MRI show nonspecific cerebral atrophy with symmetrically enlarged ventricles and prominent cortical sulci.

Alzheimer disease

Autosomal-dominant disorder presenting in early to middle adulthood with dementia and rapid, jerky, continuous choreiform movements.

Huntington disease

Pathologic hallmark is atrophy of the caudate nucleus and putamen.

Huntington disease

CT shows focal dilation of the frontal horns with loss of their normal concave shape; generalized ventricular and sulcal enlargement may also occur.

Huntington disease

Progressive degenerative "shaking palsy" beginning in middle or later life with a very gradual, prolonged course.

Parkinson disease

Stooped posture, stiffness, slow movement, fixed facial expression, and rhythmic limb tremor that disappears with voluntary movement.

Parkinson disease

Isolated loss of cerebellar tissue caused by inheritance, degeneration, or prolonged toxic exposure to alcohol or phenytoin.

Cerebellar atrophy

Sagittal MRI may show dramatic loss of substance in the cerebellar vermis, especially with severe alcoholism.

Cerebellar atrophy

Idiopathic Lou Gehrig disease with widespread selective atrophy and loss of motor nerve cells, leading to extensive paralysis.

Amyotrophic lateral sclerosis

Death usually results from respiratory weakness or aspiration pneumonia.

Amyotrophic lateral sclerosis

Dilation of the ventricular system, usually with increased intracranial pressure, caused by disturbed cerebrospinal-fluid circulation.

Hydrocephalus

Cerebrospinal-fluid flow is blocked somewhere along its normal path.

Noncommunicating (obstructive) hydrocephalus

Cerebrospinal fluid reaches the extraventricular subarachnoid space, but ventricular dilation still develops.

Communicating hydrocephalus