1,240 articles
D341 Med
D341 Med (D-341 Med, CVCL_0018, ATCC HTB-187) is a human group 3 medulloblastoma cell line established in 1988 from a 3.5-year-old boy's cerebellar tumor, grown in suspension spheroids with 20-fold c-myc amplification.
Dark Adaptation
Dark adaptation is the slow recovery of visual sensitivity in darkness after light bleaches rhodopsin, taking 30–40 minutes, driven by the retinoid cycle, and delayed in AMD, where rod intercept time is a clinical biomarker.
Deep brain stimulation
Deep brain stimulation (DBS) is neurosurgical implantation of electrodes and a pacemaker-like neurostimulator to treat Parkinson's disease, essential tremor, dystonia, OCD, and epilepsy; FDA-approved since 1997, with the first adaptive closed-loop system approved in February 2025.
Deepak Pandya
Deepak N. Pandya (1932-2020), Indian-American neuroanatomist and physician at Bedford VA and Boston University, mapped primate cortical connections, defined core-belt auditory cortex, and was father of astronaut Sunita Williams.
Default mode network
Default mode network (DMN), also called default network, a brain network of medial prefrontal, posterior cingulate, precuneus, angular gyrus, and temporal regions active at rest and during internal thought, suppressed during attention-demanding tasks; named by Raichle et al. 2001.
Degenerative disease
A degenerative disease, also called a degenerative disorder, is one marked by progressive deterioration in how affected tissues or organs work; examples include osteoarthritis, osteoporosis, and Alzheimer disease.
Delayed encephalopathy due to carbon monoxide poisoning
Delayed encephalopathy due to carbon monoxide poisoning, also called delayed neuropsychiatric sequelae, is a rare neurological disorder that emerges weeks after apparent recovery from carbon monoxide poisoning, causing cognitive impairment, personality changes, and parkinsonism.
Delta wave
Delta wave: high-amplitude 1–4 Hz (band 0.1–<4 Hz) EEG rhythm dominating N3 slow-wave sleep; also seen in anesthesia and coma, generated by thalamic h-current/T-current interactions and cortical layer 5 circuits; named by Walter in 1936.
Demecarium
Demecarium (demecarium bromide, Humorsol, Tosmilen, BC-48) is a long-acting cholinesterase inhibitor miotic for glaucoma, FDA approved 1959 and now discontinued; it survives in veterinary use via compounding pharmacies.
Dementia due to Down syndrome
Dementia due to Down syndrome (ICD-11 6D85.9) is an Alzheimer-like neurodegenerative disorder caused by chromosome 21 triplication and APP overexpression; dementia prevalence rises from about 3.4% at ages 30-39 to roughly 70% after age 50.
Dendritic spine
Dendritic spines (espinas) are small actin-rich protrusions on neuronal dendrites forming the postsynaptic side of most excitatory synapses; discovered by Cajal in 1888, they number 1-10 per micrometer and remodel during learning, aging, and disease.
Dentate gyrus
Dentate gyrus, hippocampal subregion and input channel of the hippocampal formation; three-layered cortex with granule cells, mossy fibers to CA3, adult neurogenesis in the subgranular zone, and a debated role in pattern separation.
Depolarization
Depolarization is the shift of a cell's membrane potential toward less negative values, mainly via cation influx. Key in action potentials (−70 mV to +30 mV), EPSPs, depolarizing GABA, and spreading depolarization in brain injury.
Dermatome (anatomy)
Dermatome (anatomy): area of skin innervated by one spinal dorsal root, mapped by Keegan and Garrett (1948) and Foerster (1933); adjacent dermatomes overlap, and maps guide radiculopathy and spinal cord injury localization.
Development of the human spinal cord
The human spinal cord develops from the neural tube in the fourth week of embryonic life, then ascends within the vertebral canal to end near L1 in adults.
Development of the nervous system in humans
Development of the human nervous system (neurulation): neural tube and neural crest form from ectoderm 2–3 weeks after conception; tube becomes CNS, crest builds PNS; synapses peak at ~150% adult levels in infancy.
Diabetic cataract
Diabetic cataract: lens opacity occurring earlier and more often in diabetes (2-5 fold risk), driven by polyol-pathway sorbitol and oxidative stress; surgery carries higher complication and retinopathy-progression risks.
Diabetic retinopathy
Diabetic retinopathy, a microvascular complication of diabetes damaging retinal blood vessels, progresses from nonproliferative disease to proliferative DR and diabetic macular edema; treated with anti-VEGF injections, laser photocoagulation, and vitrectomy.
Diagnosis of brain tumors
The diagnosis of brain tumors is a stepwise workup: CT and contrast-enhanced MRI characterize a suspected mass, and biopsy with molecular profiling assigns type and grade.
Diffuse axonal injury
Diffuse axonal injury (DAI), also called traumatic axonal injury (TAI), is widespread white-matter axon rupture from acceleration-deceleration forces in TBI; graded by Adams system, best seen on MRI/SWI, diagnosed in 40-50% of hospitalized TBI.
Diffuse Noxious Inhibitory Control
Diffuse noxious inhibitory control (DNIC), termed conditioned pain modulation (CPM) in humans, is a pain-inhibits-pain mechanism described by Le Bars in 1979, mediated by a brainstem spino-bulbo-spinal loop acting on wide dynamic range neurons.
DIPG trial
DIPG trial: clinical studies for diffuse intrinsic pontine glioma (DIPG), a fatal pediatric brainstem tumor. Key trials include hypofractionated radiotherapy comparisons, BIOMEDE targeted therapy, NCT03620032 re-irradiation, and CAR T studies.
Diplopia
Diplopia (double vision): perception of two images of one object. Monocular diplopia persists with one eye open (cataract, astigmatism); binocular diplopia resolves when either eye closes and signals ocular misalignment, from decompensated phoria to cranial nerve palsy.
Discectomy
Discectomy: surgical removal of herniated disc material pressing on spinal nerves, first performed planned in 1932; evolved into microdiscectomy (Yasargil, 1977) and endoscopic techniques; relieves sciatica faster than non-surgical care short-term.
Dislocation of lens
Dislocation of lens (ectopia lentis): displacement of the eye's crystalline lens from zonular weakness or rupture. Subluxation is partial, luxation complete; trauma is the most common cause, FBN1/Marfan syndrome the leading genetic cause.
Disorders of Eustachian tube
Disorders of Eustachian tube (ICD-11 AB10) cover Eustachian tube dysfunction and related conditions. ETD has three subtypes (dilatory, baro-challenge-induced, patulous), affects about 1% of adults, and is diagnosed clinically without a gold-standard test.
Dix–Hallpike test
Dix–Hallpike test (also Dix-Hallpike maneuver, Hallpike-Dix test): bedside head-positioning test introduced by Dix and Hallpike in 1952; gold standard for diagnosing posterior canal BPPV via provoked positional nystagmus resolving within 60 seconds.
Dorsal cochlear nucleus
Dorsal cochlear nucleus (DCN), part of the cochlear nucleus with the ventral cochlear nucleus; a laminar, cerebellum-like auditory brainstem nucleus processing spectral cues for sound localization and implicated in tinnitus and hyperacusis.
Dorsal column–medial lemniscus pathway
Dorsal column–medial lemniscus (DCML) pathway: ascending CNS tract carrying fine touch, vibration, two-point discrimination, and conscious proprioception from the body (excluding the face) via dorsal root ganglion, dorsal column nuclei, medullary decussation, thalamic VPL, to postcentral gyrus.
Dorsal root ganglion
Dorsal root ganglion (DRG, spinal ganglion): cluster of pseudo-unipolar sensory neuron cell bodies in each spinal nerve's dorsal root, within the neuroforamen; also the stimulation target FDA-approved in 2016 for chronic CRPS pain.