1,240 articles
Periglomerular cell
Periglomerular cell (PG cell, juxtaglomerular interneuron): small GABAergic interneuron surrounding olfactory bulb glomeruli, soma 5–10 µm, uniglomerular dendrites, dendrodendritic inhibition of mitral/tufted cells, dopaminergic TH+ subtype, adult-born, distinct from renal periglomerular usage.
Perinatal asphyxia
Perinatal asphyxia (birth asphyxia) is hypoxic-ischemic organ injury near delivery, causing about 900,000 neonatal deaths yearly; its brain form is HIE, treated with 72-hour therapeutic hypothermia at 33.5–34.5 °C.
Periorbital cellulitis
Periorbital (preseptal) cellulitis: bacterial infection of the eyelid and surrounding skin anterior to the orbital septum, distinct from orbital cellulitis; normal vision and eye movement, treated with oral or IV antibiotics.
Periorbital puffiness
Periorbital puffiness, or periorbital edema (bags under the eyes), is swelling around the eye orbit from fluid, fat or inflammation; causes range from aging, salt, sleep loss and allergies to cellulitis, thyroid or renal disease.
Peripheral vision
Peripheral vision is sight outside the fovea, covering about 99.9% of the visual field. Also called indirect or eccentric vision, it is limited mainly by crowding, not blur, and excels at motion and scene gist.
Periventricular leukomalacia
Periventricular leukomalacia (PVL), also called encephalopathy of prematurity, is white matter death around the brain ventricles in premature infants, caused by ischemia and infection, diagnosed by ultrasound or MRI, and strongly linked to cerebral palsy.
Permanent vegetative state
Permanent vegetative state, also called chronic VS or unresponsive wakefulness syndrome, is a prognosis of irreversible wakeful unawareness after severe brain injury, declared 3 months (nontraumatic) or 12 months (traumatic) after onset.
Perrault syndrome
Perrault syndrome, also called XX gonadal dysgenesis with deafness, is a rare autosomal recessive disorder causing sensorineural hearing loss in both sexes and ovarian dysfunction in 46,XX females, caused by biallelic variants in 12 genes, mostly mitochondrial.
Persistent placoid maculopathy
Persistent placoid maculopathy (PPM) is a rare idiopathic bilateral chorioretinopathy with well-defined white plaque-like macular lesions, first described in 2007, most often affecting Caucasian men in their 50s and 60s.
Peters anomaly
Peters anomaly (irido-corneo-trabecular dysgenesis): rare congenital anterior segment dysgenesis causing central corneal opacity with posterior stromal and Descemet defect; types I and II, FOXC1/PAX6/PITX2/CYP1B1 genes, frequent glaucoma, keratoplasty outcomes.
Petrositis
Petrositis, or petrous apicitis, is rare suppuration of the petrous apex of the temporal bone from spreading otitis media, causing Gradenigo's syndrome: otorrhea, trigeminal facial pain, and abducens palsy. Treated with broad-spectrum antibiotics, surgery if unresponsive; ICD-10 H70.2, ICD-11 AB11.2.
Phantom limb
Phantom limb: perception that an amputated or congenitally missing limb is still present, causing phantom limb sensation (PLS) and phantom limb pain (PLP) in most amputees; mechanisms include neuromas and cortical reorganization; treatments include mirror therapy, GMI, VR, and rTMS.
Phantom pain
Phantom pain, also called phantom limb pain, is pain felt in an amputated or missing body part, affecting most amputees and often treated with mirror therapy.
Pharyngeal reflex
Pharyngeal reflex (gag reflex): involuntary throat contraction protecting the airway, mediated by CN IX afferent and CN X efferent limbs; poorly predictive of dysphagia despite traditional bedside use.
Phenylthiocarbamide
Phenylthiocarbamide (PTC, phenylthiourea), a synthetic bitter compound whose bimodal tasting ability, controlled by TAS2R38 variants, made it a classic human Mendelian trait discovered in 1931.
Phineas Gage
Phineas Gage (1823–1860), American railroad foreman whose 1848 Cavendish, Vermont tamping-iron injury caused frontal lobe damage with reported personality change; famous case in neuroscience, skull and iron at Harvard.
Photokeratitis
Photokeratitis (ultraviolet keratitis, arc eye, snow blindness) is a painful, usually bilateral corneal epithelial injury from UV exposure, with delayed onset 6-12 hours and self-healing within 24-72 hours.
Photoreceptor cell
Photoreceptor cells (rods and cones) are retinal neurons that convert light into electrical signals via a G-protein phototransduction cascade; rods detect single photons in dim light, cones mediate bright-light, color, high-acuity vision.
Photoreceptor disk component PRCD
PRCD (photoreceptor disc component) is a 54-amino-acid, ~6 kDa rhodopsin-binding protein of unknown function found only in photoreceptor outer segment discs; its C2Y mutation causes canine progressive rod-cone degeneration and human retinitis pigmentosa 36.
Photorefractive keratectomy
Photorefractive keratectomy (PRK) is a type of refractive surgery that uses an excimer laser to reshape the cornea, without a flap, correcting myopia, hyperopia, and astigmatism.
Phrenic nerve
Phrenic nerve (nervus phrenicus): bilateral mixed nerve from C3-C5 (mainly C4) that is the sole motor supply of the diaphragm and sensory nerve of its center, pericardium, and mediastinal pleura; injury causes hemidiaphragm paralysis.
Physiologic anisocoria
Physiologic anisocoria, also called simple or essential anisocoria, is benign unequal pupil size of 1 mm or less, equal in light and dark, affecting up to 20% of people and requiring no treatment.
Physiology & behavior
Physiology & Behavior is a peer-reviewed academic journal published by Elsevier that covers the causal physiological mechanisms of behavior; it was founded in 1966 by Pergamon Press.
Pigmentary open-angle glaucoma
Pigmentary open-angle glaucoma (pigmentary glaucoma, PG): secondary open-angle glaucoma from pigment dispersion syndrome, affecting young myopic men, with higher surgery rates and LTP/MIGS failure than POAG.
Pikachurin
Pikachurin (EGFLAM) is an extracellular matrix protein of the photoreceptor ribbon synapse cleft, identified in 2008, that binds alpha-dystroglycan via LG2-LG3 domains and GPR179, aligning bipolar dendrites; its loss disrupts retinal signaling.
Pilocarpine
Pilocarpine, a plant-derived muscarinic cholinergic agonist introduced to ophthalmology in 1876, lowers intraocular pressure in glaucoma and, in low concentrations (Vuity 1.25%, Qlosi 0.4%), treats presbyopia; limited today by miosis, blurred vision, and frequent dosing.
Pilocytic astrocytoma
Pilocytic astrocytoma, also known as juvenile pilocytic astrocytoma, is a slow-growing grade 1 glioma, the most common brain tumor in children, with 90% ten-year survival.
Pinguecula
Pinguecula: a common benign yellow-white raised growth on the conjunctiva near the limbus, caused by UV, wind, and dust; unlike pterygium it never invades the cornea and is usually asymptomatic.
Piriformis syndrome
Piriformis syndrome, also called deep gluteal syndrome, is sciatic nerve compression by the piriformis muscle causing buttock pain radiating down the leg; treated first with stretching, NSAIDs, injections, and rarely surgery.
Pitch and loudness coding in the auditory system
Pitch and loudness coding in the auditory system is how frequency and intensity are represented via cochlear place codes and phase-locked spike timing, which fails above a few kHz.