26 - Central Nervous System

Red neurons

Earliest morphologic marker of neuronal cell death or acute neuronal injury

Gliosis - astrocytic hyperplasia and hypertrophy

Most important pathologic marker of CNS injury

Vasogenic edema

Type of cerebral edema observed in infection, inflammation and tumors occurring due to increased vascular permeability

Cytotoxic edema

Type of cerebral edema observed in generalized hypoxic injury where the ionic balance of cells are disrupted

Communicating hydrocephalus

Type of hydrocephalus which occurs due to ↓ CSF resorption by arachnoid granulations i.e., in healed subarachnoid hemorrhage

Noncommunicating hydrocephalus

Type of hydrocephalus when a focal obstruction within the ventricular system is present

Anterior cerebral artery

Cerebral artery compressed in subfalcine herniation

Ipsilateral CN III and Posterior cerebral artery (PCA), and cerebral peduncle

Neurovascular structures compressed in transtentorial (uncal) herniation

Duret hemorrhages

Linear/Flame-shaped hemorrhagic lesions in midbrain/pons

Brainstem

Compression of this structure in tonsillar herniation causes cardiac and respiratory depression

Spinal dysraphism (Spina bifida)

Most common CNS malformation

Folic acid

Deficiency of this vitamin is a known risk factor for NTDs

Myelomeningocele

Extension of spinal cord and meninges through a vertebral column defect

Occiput

Most common site of encephalocele

Anencephaly

This cranial dysraphism occurs due to a failure in the closure of the anterior neural tube

Holoprosencephaly

Incomplete separation of cerebral hemispheres across midline

Agenesis of corpus callosum

Absence of white matter bundles that carry cortical projections from one hemisphere to another

Chiari II Malformation (Arnold-Chiari)

Small posterior fossa causing downward extension of cerebellar tonsils and medulla through the foramen magnum

Chiari I Malformation

Low-lying cerebellar tonsils through foramen magnum

Dandy-Walker malformation

Hypoplasia/agenesis of the vermis resulting in cystic enlargement of 4th ventricle

Syringomyelia

Fluid-filled cavity in the inner portion of the cord

Hematogenous

Most common route of CNS infection

Rabies, VZV

Viruses with retrograde spread in the nervous system

S. pneumoniae

Most common cause of acute pyogenic meningitis overall

Group B streptococci, S. pneumoniae, L. monocytogenes, E. coli

Common etiologies of acute pyogenic meningitis in newborns

N. meningitidis, S. pneumonia

Common etiologies of acute pyogenic meningitis in teen and young adults

Enteroviruses

Most identifiable agent of acute aseptic meningitis

Tuberculous meningitis

CSF protein and mononuclear cells are markedly elevated in this type of meningitis

Acute bacterial endocarditis, Congenital heart disease (R→L shunts), Chronic pulmonary infections, Immunosuppression

Risk factors for brain abscess formation

Obliterative endarteritis, Perivascular plasma cells, Gummas

Morphologic findings in meningovascular neurosyphilis

HSV

Virus associated with hemorrhagic necrotizing encephalitis of the temporal lobe

CMV

Virus associated with microcephaly, periventricular calcification

Negri bodies

Cytoplasmic, round, eosinophilic inclusions in pyramidal neurons of the hippocampus and Purkinje cells of the cerebellum in rabies infection

C. neoformans

Most common cryptococcal infection in immunosuppressed patients

Anterior skull base

Location of skull fracture associated with Raccoon sign and CSF rhinorrhea

Central skull base

Location of skull fracture associated with CN III, IV, V, VI injuries, Carotid injury

Temporal fracture

Most common type of skull fracture

Battle sign

Mastoid hematoma

Epidural hematoma

Rapid neurologic deterioration with lucid intervals

Middle meningeal artery

Blood vessel lacerated in epidural hematoma

Lentiform hyperdense lesion

CT scan finding in epidural hematoma

Bridging veins

Blood vessel lacerated in subdural hematoma

Crescent-shaped hyperdense lesion

CT scan finding in subdural hematoma

C4

Above which cervical vertebra is respiratory compromise expected in cases of spinal cord injury

Pyramidal neurons of Hippocampus (Area CA1: Sommer sector), Cerebellar Purkinje cells, Pyramidal neurons in cerebral cortex (Layers III and IV)

Neurons most susceptible to ischemic injury

ACA-MCA border

Most common location of watershed infarcts in global cerebral ischemia

Putamen

Most common site of deep parenchymal hemorrhage

Cerebral amyloid angiopathy - Amyloid (Aβ) deposits in vascular wall

Etiology of lobar hemorrhage

Saccular "Berry" Aneurysm

Most common type of intracranial aneurysm; Most common cause of spontaneous subarachnoid hemorrhage (SAH)

Circle of Willis - ACA-ACoA junction (40%)

Most common site of berry aneurysm

ADPKD, Ehler-Danlos (Type IV), NF1, Marfan, Fibromuscular dysplasia, Coarctation of aorta

Associated conditions with berry aneurysm

Arteriovenous malformation

Most common clinically significant vascular malformation

MCA territory

Usual site of AV malformation

Multiple sclerosis

A patient presents with multiple neurologic deficits separated in time and space and optic neuritis; CSF findings include moderate pleocytosis, mildly ↑ protein, ↑ IgG. What is the most likely diagnosis?

Oligoclonal IgG bands

CSF electrophoresis finding in multiple sclerosis

Jacksonian march

Partial seizure that starts with one group of muscles then spreads "marches" to other groups of muscles

Cerebral pontine myelinolysis

Disease associated with rapid correction of hyponatremia

Creutzfeldt-Jakob disease (CJD)

Most common prion disease

Kuru plaques

Central core with radiating spicules of amyloid seen in the cerebellum of CJD patients

Alzheimer disease (AD)

Most common cause of dementia in older adults

Trisomy 21, apoE (ε4) allele (Ch19)

Associations with Alzheimer disease

Neuritic plaques (Aβ)

Focal spherical collections of dilated, tortuous axonal or dendritic process around a central amyloid core; Specific for AD

Neurofibrillary tangles (Ta)

Basophilic fibrillary structures; Not specific for AD but correlates better with degree of dementia

Parkinson disease

A patient presents with diminished facial expression, slow movement, stooped posture, festinating gait, rigidity, pill-rolling tremor. What is the most likely diagnosis?

Gaucher disease (Glucocerebrosidase)

Most important risk factor for Parkinson disease

Lewy body (α-synuclein)

Cytoplasmic, eosinophilic, round to elongated inclusions with a dense core and surrounding pale halo seen in Parkinson disease

Dementia with Lewy bodies

Parkinsonism + dementia + visual hallucination

CAG

Trinucleotide repeated or expanded in Huntington disease

Pneumonia

Most common immediate cause of death

Thiamine

Vitamin deficiency in Wernicke encephalopathy and Korsakoff syndrome

Wernicke encephalopathy

Triad of ataxia, confusion, ophthalmoplegia

Korsakoff syndrome

Triad of confabulation, hallucination, amnesia

Glioma

Most common group of primary brain tumors

Glioblastoma multiforme

Most common primary malignant brain tumor in adults

Oligodendroglioma

Brain glioma with fried egg appearance of the tumor cells and chicken-wire appearance of the vasculature

IDH1 or IDH2 mutation AND 1p/19q codeletion

Etiology of oligodendroglioma

Astrocytoma

Most common type of glioma

Pilocytic astrocytoma

Most common glioma in children; (+) Rosenthal fibers

Ependymoma

Perivascular pseudorosettes are seen in which brain tumor

Medulloblastoma

2nd most common primary malignant tumor in children; (+) Homer-Wright pseudorosettes; (+) Drop metastasis

Metastasis

Most common CNS neoplasm in adults

Primary CNS lymphoma

Most common CNS neoplasm in immunocompromised individuals