In dieser Lektion befinden sich 115 Karteikarten
USMLE First Aid
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- Pilocytic (low-grade) astrocytoma - Most common 1° brain tumor in childhood.- Usually well circumscribed.- In children, most often found in posterior fossa (eg, cerebellum).- May be supratentorial.- Benign, good prognosis. - Glial cell ...
- Medulloblastoma - Most common malignant brain tumor in childhood. - Commonly involves cerebellum.- Can compress 4th ventricle, causing noncommunicating hydrocephalus → headaches, papilledema.- Can send "drop metastases" ...
- Ependymoma - Most commonly found in 4th ventricle.- Can cause hydrocephalus.- Poor prognosis. - Ependymal cell origin.- Characteristic perivascular pseudorosettes.- Rod-shaped blepharoplasts (basal ciliary bodies) ...
- Craniopharyngioma - Most common childhood supratentorial tumor.- May be confused with pituitary adenoma (both can cause bitemporal hemianopia). - Derived from remnants of Rathke pouch (ectoderm).- Calcification is common.- ...
- Pinealoma Tumor of pineal gland. - Can cause Parinaud syndrome: compression of tectum → vertical gaze palsy, bilateral eyelid retraction (eg, Collier sign, sclera visible above the superior corneal limbus), ...
- Glioblastoma multiforme (grade IV astrocytoma) Common, highly malignant 1° brain tumor with ~1-year median survival.- Found in cerebral hemispheres.- Can cross corpus callosum ("butterfly glioma"). - "Pseudopalisading" pleomorphic tumor cells border ...
- Oligodendroglioma Relatively rare, slow growing.- Most often in frontal lobes.- "Chicken-wire" capillary pattern. - Oligodendrocytes = "fried egg" cells – round nuclei with clear cytoplasm.- Often calcified.
- Meningioma Common, typically benign brain tumor.- Females > males.- Most often occurs near surfaces of brain and parasagittal region.- Extra-axial (external to brain parenchyma) and may have a dural attachment ("tail"). ...
- Syringomyelia Cystic cavity within central canal of spinal cord (syringobulbia if in medulla). - Fibers crossing in anterior white commissure (spinothalamic tract) are typically damaged first. Results in a "cape-like," ...
- Acetylcholine Location of synthesis: Basal nucleus of Meynert ↓ Alzheimer disease ↓ Huntington disease ↑ Parkinson disease
- Dopaminergic pathways Mesocortical: ↓ activity → "negative" symptoms (eg, anergia, apathy, lack of spontaneity).- Antipsychotic drugs have limited effects. Mesolimbic: ↑ activity → "positive" symptoms (eg, delusions, ...
- Athetosis Slow, writhing, snake-like movements; especially seen in fingers. - Lesion in basal ganglia (eg, Huntington)
- Chorea Sudden, jerky, purposeless movements - Lesion in basal ganglia - Chorea = dancing- Seen in Huntington disease and in acute rheumatic fever (Sydenham chorea).
- Dystonia Sustained, involuntary muscle contractions - Writer's cramp, blepharospasm
- Tremor Essential tremor:- High-frequency tremor with sustained posture (eg, outstretched arms), worsened with movement or when anxious.- Often familial. Patients often self-medicate with alcohol, which ↓ ...
- Hemiballismus Sudden, wild flailing of 1 arm +/- ipsilatreal leg - Lesion in contralateral subthalamic nucleus (eg, lacunar stroke)
- Myoclonus Sudden, brief, uncontrolled muscle contraction Jerks, hiccups, common in metabolic abnormalities such as renal and liver failure
- Parkinson disease Degenerative disorder of CNS associated with Lewy bodies (composed of α-synuclein – intracellular eosinophilic inclusions) and loss of dopaminergic neurons (ie, depigmentation) of substantia nigra ...
- Huntington disease Autosomal dominant trinucleotide (CAG)n repeat expansion in the huntingtin (HTT) gene on chromosome 4. Expansion of the protein's polyglutamine region results in a gain-of-function that leads to pathological ...
- Osmotic demyelination syndrome (central pontine myelinolysis) ... Massive axonal demyelination in pontine white matter 2° to osmotic changes, most commonly iatrogenic correction of hyponatremia but also rapid shifts of other osmolytes (eg, glucose). - Acute paralysis, ...
- Multiple sclerosis Autoimmune inflammation and demyelination of CNS (brain and spinal cord) with subsequent axonal damage. Can present with:- Acute optic neuritis (sudden unilateral visual loss of vision associated with Marcus ...
- Acute inflammatory demyelinating polyradiculopathy Most common subtype of Guillain-Barré syndrome.Autoimmune condition associated with infections (eg, Campylobacter jejuni, viruses [eg, Zika]) that destroys Schwann cells by inflammation and demyelination ...
- Progressive multifocal leukoencephalopathy Demyelination of CNS due to destruction of oligodendrocytes (2° to reactivation of latent JC virus infection). - Seen in 2-4% of AIDS patients. - Rapidly progressive, usually fatal. - Predominantly involves ...
- Sturge-Weber syndrome (encephalotrigeminal angiomatosis) ... Congenital, non-inherited (sporadic), developmental anomaly of neural crest derivatives due to somatic mosaicism for an activating mutation in one copy of the GNAQ gene. - Affects small (capillary-sized) ...
- Tuberous sclerosis TSC1 mutation on chromosome 9 or TSC2 mutation on chromosome 16. Tumor suppression genes.- Autosomal dominant, variable expression. - Hamartomas in CNS and skin- Angiofibromas- Mitral regurgitation- ...
- Neural development Notochord induces overlying ectoderm to differentiate into neurectoderm and form neural plate.Neural plate gives rise to neural tube and neural crest cells.Notochord becomes nucleus pulposus of intervertebral ...
- Central and peripheral nervous system origins Neuroepithelia in neural tube – CNS neurons, ependymal cells (inner lining of ventricles, make CSF), oligodendrocytes, astrocytes. Neural crest – PNS neurons, Schwann cells. Mesoderm – Microglia ...
- Neural tube defects Neuropores fail to fuse (4th week) → persistent connection between amniotic cavity and spinal canal. Associated with maternal diabetes as well as low folic acid intake before conception and during ...
- Holoprosencephaly Failure of left and right hemispheres to separate; usually occurs during weeks 5-6. - May be related to mutations in sonic hedgehog signaling pathway. - Moderate form has cleft lip/palate, most severe ...
- Posterior fossa malformations Chiari I malformation: Ectopia of cerebellar tonsils (1 structure). Congenital, usually asymptomatic in childhood, manifests in adulthood with headaches and cerebellar symptoms. Associated with spinal ...
- Sensory receptors Free nerve endings:- C – slow, unmyelinated fibers- Aδ – fast, myelinated fibers- All skin, epidermis, some viscera- Senses: pain, temperature Merkel discs:- Large, myelinated fibers; adapt slowly- ...
- Blood-brain barrier Prevents circulating blood substances (eg, bacteria, drugs) from reaching CSF/CNS. Formed by 3 structures:- Tight junctions between nonfenestrated capillary endothelial cells- Basement membrane- Astrocyte ...
- Hypothalamus Inputs (areas not protected by BBB): OVLT (senses change in osmolarity), area postrema (found in medulla, responds to emetics). Lateral area: Hunger. Destruction → anorexia, failure to thrive. Stimulated ...
- Sleep physiology Sleep cycle is regulated by the circadian rhythms, which is driven by suprachiasmatic nucleus (SCN) of hypothalamus. Circadian rhythm controls nocturnal release of ACTH, prolactin, melatonin, norepinephrine: ...
- Thalamus Major relay for all ascending sensory information except olfaction. Ventral posteriolateral nucleus (VPL):- Spinothalamic and dorsal columns/medial lemniscus- Vibration, pain, pressure, proprioception, ...
- Limbic system Collection of neural structures involved in emotion, long-term memory, olfaction, behavior modulation, ANS function. Consists of hippocampus, amygdalae, mammillary bodies, anterior thalamic nuclei, cingulate ...
- Cerebellum Modulates movement; aids in coordination and balance. Input:- Contralateral cortex via middle cerebellar peduncle.- Ipsilateral proprioceptive information via inferior peduncle from spinal cord. Output: - ...
- Basal ganglia Important in voluntary movements and making postural adjustments.Receives cortical input, provides negative feedback to cortex to modulate movement. Striatum = putamen (motor) + caudate (cognitive).Lentiform ...
- Vagal nuclei Nucleus solitarius: - Visceral sensory information (eg, taste, baroreceptors, gut distension)- Cranial nerves: VII, IX, X Nucleus ambiguus:- Motor innervation of pharynx, larynx, upper esophagus (eg, ...
- Spinal nerves There are 31 pairs of spinal nerves in total: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal. Nerves C1-7 exit above corresponding vertebra. C8 spinal nerve exists below C7 and above T1. All ...
- Landmark dermatomes C2: Posterior half of the skullC3: High turtleneck shirtC4: Low-collar shirtC6: Includes thumbsT4: At the nippleT7: At the xiphoid processT10: At the umbilicus. Important point of referred pain in early ...
- Common brain lesions Frontal lobe: Disinhibition and deficits in concentration, orientation, judgment; may have reemergence of primitive reflexes. Frontal eye fields: Eyes look toward (destructive) side of lesion. In seizures ...
- Ischemic brain disease/stroke Irreversible damage begins after 5 minutes of hypoxia. Most vulnerable: hippocampus, neocortex, cerebellum, watershed areas. Stroke imaging: noncontrast CT to exclude hemorrhage (before tPA can be given). ...
- Epidural hematoma Rupture of middle meningeal artery (branch of maxillary artery), often 2° to skull fracture involving the pterion (thinnest area of the lateral skull). - Lucid interval. - Scalp hematoma and rapid intracranial ...
- Subdural hematoma Rupture of bridging veins. - Can be acute (traumatic, high-energy impact → hyperdense on CT) or chronic (associated with mild trauma, cerebral atrophy, elderly, alcoholism → hypodense on CT). Also ...
- Subarachnoid hemorrhage Bleeding due to trauma, or rupture of an aneurysm (such as a saccular aneurysm) or arteriovenous malformation.- Rapid time course. - Patients complain of "worst headache of my life." - Bloody or yellow ...
- Intraparenchymal hemorrhage Most commonly caused by systemic hypertension. - Also seen with amyloid angiopathy (recurrent lobar hemorrhagic stroke in elderly), vasculitis, neoplasm. - May be 2° to reperfusion injury in ischemic ...
- Effects of strokes - Anterior circulation Mittel cerebral artery:- Area: Motor and sensory cortices – upper limb and face. Temporal lobe (Wernicke area); frontal lobe (Broca area).- Symptoms: Contralateral paralysis and sensory loss – face ...
- Aneurysms Saccular (berry) aneurysm: Occurs at bifurcations in the circle of Willis. Most common site is junciton of ACom and ACA. Associated with ADPKD, Ehlers-Danlos syndrome. Other risk factors: advanced age, ...
- Seizures Characterized by synchronized, high-frequency neuronal firing. Variety of forms. Partial (focal) seizures: Affect single area of the brain. Most commonly originate in medial temporal lobe. Often preceded ...