1,240 articles
Corneal endotheliitis
Corneal endotheliitis is inflammation centered on the corneal endothelium, the cell layer keeping the cornea clear, causing corneal edema; most cases are viral, chiefly herpesviruses like cytomegalovirus, and delayed treatment risks irreversible endothelial cell loss.
Corneal reflex
The corneal reflex, also called the blink reflex, closes both eyelids when the cornea is touched, protecting the eye and testing cranial nerves V and VII.
Corneal tattooing
Corneal tattooing, or keratopigmentation, deposits pigment into the corneal stroma to disguise corneal scars, mask iris-defect symptoms, or change eye color; practiced since Galen, modernized by Von Wecker in 1869, with no FDA-approved pigments.
Corneal transplantation
Corneal transplantation (keratoplasty) replaces diseased corneal tissue with donor cornea. First done by Eduard Zirm in 1905; types include PK, DALK, DSAEK, and DMEK; global supply is 1 cornea per 70 needed.
Corneal ulcer
Corneal ulcer (ulcerative keratitis): an open sore on the cornea, usually infectious (bacterial, viral, fungal, Acanthamoeba), an ocular emergency. Contact lens wear is the leading risk factor; treated with intensive topical antibiotics.
Corona radiata
The corona radiata is the fan-shaped sheet of white matter projection fibers going to and from the cerebral cortex, radiating from and converging downward into the internal capsule.
Corpus callosotomy
Corpus callosotomy, or split-brain surgery, is palliative neurosurgery dividing the corpus callosum for drug-resistant epilepsy, chiefly atonic drop attacks; first done by van Wagenen in 1940, with open, endoscopic, and laser variants.
Corpus callosum
Corpus callosum: the brain's largest white matter commissure, about 190 million axons linking the hemispheres, unique to placental mammals; key biomarker in MS, aging, and agenesis (1:4000 births).
Correction of Hearing Impairment
Correction of Hearing Impairment (MeSH D012048, aural rehabilitation) covers procedures for correcting hearing disorders: hearing aids, cochlear implants, and aural rehabilitation, with entry terms including Audiologic Rehabilitation and Aural Habilitation.
Cortical homunculus
Cortical homunculus, or sensory and motor homunculus (Latin 'little man'): distorted body maps on the primary somatosensory and motor cortices, first drawn by Wilder Penfield and Edwin Boldrey from 1937 electrical-stimulation studies of awake epilepsy patients.
Cortical interneuron
Cortical interneuron: GABAergic inhibitory neuron of the cerebral cortex, 20-30% of cortical neurons, in PV, SST, and 5HT3aR classes, born mainly in the ganglionic eminences.
Cortical Synchronization
Cortical synchronization, or neural phase synchronization, is the phase locking of cortical oscillations between brain regions, studied via PLV, coherence, and phase lag index in EEG and MEG as a mechanism for large-scale integration, memory, and attention, with volume conduction as its main measurement artifact.
Corticobasal degeneration
Corticobasal degeneration (CBD), also called corticobasal syndrome (CBS) in its clinical form, is a rare 4-repeat tauopathy causing asymmetric rigidity, apraxia, dystonia, and myoclonus, with onset around age 64, mean survival 6.5 years, and no disease-modifying treatment.
Corticobulbar tract
Corticobulbar tract (corticonuclear tract): descending pyramidal-tract pathway from the motor cortex through the internal capsule and brainstem to cranial nerve motor nuclei, bilaterally innervating most nuclei except the lower facial and hypoglossal nuclei.
Corticospinal tract
Corticospinal tract (pyramidal tract): major descending pathway for voluntary movement, from frontoparietal cortex through internal capsule to spinal cord; 75-90% of fibers cross at the medullary pyramidal decussation.
Cotton wool spots
Cotton wool spots (CWS) are fluffy yellow-white retinal lesions of accumulated axoplasmic debris in the nerve fiber layer, signaling ischemia from diabetes, hypertension, HIV, vein occlusion, or emboli; usually resolving in 6-12 weeks.
Coup contrecoup injury
Coup contrecoup injury: paired focal brain contusions at and opposite the site of a head blow, caused by brain-skull contact during rapid acceleration or deceleration; mechanisms include pressure gradients, cavitation, and rotation, distinguishing it from diffuse axonal injury.
Couvade syndrome
Couvade syndrome, also called sympathetic pregnancy, causes expectant fathers to experience pregnancy-like symptoms such as weight gain and nausea, which typically cease after the child's birth.
Cranial nerves
Cranial nerves: twelve paired nerves (I–XII, plus controversial cranial nerve zero) emerging from the brain and brainstem, innervating head and neck structures, with nuclei organized in sensory and motor columns in the brainstem.
Craniopharyngioma
Craniopharyngioma, a rare benign sellar/suprasellar brain tumor from Rathke's pouch remnants; two distinct WHO 2021 entities, adamantinomatous (CTNNB1, children) and papillary (BRAF V600E, adults), treated by surgery, radiotherapy, and targeted drugs.
Craniotomy
Craniotomy: neurosurgical procedure temporarily removing a skull bone flap to reach the brain for tumor, hemorrhage, aneurysm, or seizure treatment; first wide approach by Wagner in 1889; bone replaced, unlike craniectomy.
Creutzfeldt–Jakob disease
Creutzfeldt–Jakob disease (CJD), also called classic CJD, is a rare, always fatal human prion disease causing rapidly progressive dementia, about 1–2 cases per million yearly, mostly sporadic, distinct from variant CJD linked to BSE beef.
Critical period
Critical period: a limited developmental window when experience is essential for normal brain development and its absence causes permanent change; classic model is Hubel and Wiesel's ocular dominance plasticity in cat visual cortex, distinct from broader sensitive periods.
Cross-dominance
Cross-dominance (crossed laterality, mixed dominance): dominant hand and dominant eye on opposite body sides. Affects marksmanship learning (86.1% vs 56.5% rifle qualification) but shows no reliable link to academic achievement or intelligence.
Cushing reflex
Cushing reflex (vasopressor response, Cushing reaction): physiological response to acute intracranial pressure elevation, producing Cushing's triad of widened pulse pressure, bradycardia, and irregular respirations; proposed by Harvey Cushing in 1901.
Cybathlon
Cybathlon is an international competition organized by ETH Zurich where pilots with disabilities complete everyday tasks using prostheses, exoskeletons, and brain-computer interfaces; it was first held in 2016.
Cyborg
Cyborg: a cybernetic organism, a human integrally combined with technology. Coined by Clynes and Kline in 1960 for space-flight self-regulation; today covers brain-computer implants, prosthetics, and human augmentation.
Cyclopia
Cyclopia (synophthalmia) is the most severe facial form of holoprosencephaly: a single central eye with absent nose or proboscis, caused by failed forebrain division; prevalence 1 in 100,000 births, lethal within days, linked to SHH mutations, trisomy 13, and cyclopamine.
Cystoid macular dystrophy
Cystoid macular dystrophy, also called dominant cystoid macular dystrophy (DCMD), is a rare autosomal dominant retinal disorder in which cystoid macular edema appears in childhood and progresses to macular atrophy with poor vision.
D1/D2-hybrid medium spiny neuron
D1/D2-hybrid medium spiny neuron, also called D1/D2-SPN or D1/D2-coexpressing MSN, a striatal projection neuron coexpressing dopamine D1 and D2 receptors with dynorphin and enkephalin; proposed third basal ganglia pathway bearing the D1–D2 receptor heteromer, rare but motor-functionally significant.