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Post traumatic hydrocephalus
Post-traumatic hydrocephalus (PTH), first described by Dandy in 1914, is CSF accumulation with ventricular enlargement after traumatic brain injury; incidence 0.7-51.4%, treated mainly by ventriculoperitoneal shunt.
Post-cardiac arrest syndrome
Post-cardiac arrest syndrome (PCAS) is the multiorgan condition after return of spontaneous circulation, with four components: precipitating pathology, anoxic brain injury, myocardial dysfunction, and ischemia-reperfusion injury; managed with MAP ≥65 mm Hg, temperature control 32–37.5 °C, and delayed multimodal neuroprognostication.
Post-concussion syndrome
Post-concussion syndrome (PCS), also called persistent post-concussive symptoms (PPCS), is a cluster of somatic, cognitive, sleep, and affective symptoms persisting after concussion; diagnosed by symptom report, with prevalence estimates from 11 to 82 percent depending on criteria.
Post-traumatic amnesia
Post-traumatic amnesia (PTA): post-coma state of confusion, disorientation, and anterograde/retrograde amnesia after traumatic brain injury; measured with GOAT or Westmead scales; duration classifies TBI severity and predicts outcome.
Postencephalitic parkinsonism
Postencephalitic parkinsonism (PEP), a sequela of encephalitis lethargica (von Economo's disease), is a tauopathy causing parkinsonism with oculogyric crises after the 1916-1930 epidemic; distinct from Parkinson's disease by neurofibrillary tangles and absent alpha-synuclein.
Posterior blepharitis
Posterior blepharitis (後部眼瞼炎), ICD-11 9A02.1, is inflammation of the back eyelid margin, typically meibomian gland dysfunction; treated with warm compresses, lid hygiene, and antibiotics, with no strong cure evidence.
Posterior cerebral artery
Posterior cerebral artery (PCA, arteria cerebri posterior): terminal basilar artery branch supplying occipital and temporal lobes, midbrain, thalamus; P1–P4 segments; fetal-type variant in 20–32%; PCA stroke causes homonymous hemianopia.
Posterior cruciate ligament
Posterior cruciate ligament (PCL): strongest knee ligament, behind the ACL, primary restraint to posterior tibial translation; two bundles, injured by dashboard or fall on bent knee, often treated nonoperatively.
Posterior pituitary
Posterior pituitary (neurohypophysis): neural posterior lobe of the pituitary gland, derived from hypothalamic downgrowth, storing and releasing hypothalamic vasopressin and oxytocin into the circulation.
Posterior tibial artery
Posterior tibial artery (arteria tibialis posterior): terminal branch of the popliteal artery supplying the deep posterior calf and plantar foot, palpable behind the medial malleolus, used in pulse grading and ABI measurement.
Posterior vitreous detachment
Posterior vitreous detachment (PVD), separation of the vitreous gel from the retina, an age-related cause of flashes and floaters; risk of retinal tears rises with floaters, hemorrhage, and vitreous pigment, requiring dilated examination and 6-week follow-up.
Postpartum bleeding
Postpartum bleeding (postpartum hemorrhage, PPH) is excessive bleeding after childbirth, the leading direct cause of maternal death; defined by ACOG as ≥1000 mL or hypovolemia within 24 hours, prevented with uterotonics and treated with the MOTIVE bundle and tranexamic acid.
Postprandial somnolence
Postprandial somnolence, or food coma, is drowsiness after eating, peaking 1-2 hours post-meal; caused by gut signals, metabolites, and circadian dip, not blood flow shifts.
Postural Balance
Postural balance, also called postural equilibrium, is the stable state achieved when body mass is ideally distributed, keeping the body steady while sitting, standing, or walking.
Power nap
Power nap: a short 10-30 minute daytime sleep, also called a catnap, kept in light N1-N2 sleep to boost alertness and mood while avoiding slow-wave sleep and sleep inertia; best taken in the early afternoon.
Prathap C. Reddy (ప్రతాప్ చంద్ర రెడ్డి)
Prathap C. Reddy (ప్రతాప్ చంద్ర రెడ్డి), also known as Prathap Chandra Reddy, is an Indian cardiologist who founded Apollo Hospitals, India's first corporate hospital chain, in Chennai in 1983.
Pre-ejaculate
Pre-ejaculate (pre-cum, Cowper's fluid) is clear fluid released from the penis during arousal by the bulbourethral glands; it neutralizes urethral acidity, may contain sperm, and affects withdrawal-method contraception and HIV/STI risk.
Pre-excitation syndrome
Pre-excitation syndrome, chiefly Wolff-Parkinson-White (WPW), is a cardiac condition where an accessory pathway bypasses the AV node, causing early ventricular activation, delta waves, AVRT, and risk of pre-excited atrial fibrillation; curable by catheter ablation.
Prefrontal cortex
Prefrontal cortex (PFC): the anterior frontal-lobe region supporting executive function, working memory, and socio-emotional behavior; about 30% of human cortical surface, matures into early adulthood, and is implicated in autism and schizophrenia.
Preload (cardiology)
Preload (cardiology): the end-diastolic load on a heart ventricle, defined as passive wall stress at end-diastole and clinically surrogated by EDV or EDP. Central to the Frank–Starling law and to fluid responsiveness testing (PLR, PPV, EEO, mini-fluid challenge) in critical care.
Premature closure of the arterial duct
Premature closure of the arterial duct (ductus arteriosus), ORPHA:95486, ICD-10 Q25.8: rare fetal constriction or closure of the duct without structural heart defects, usually from maternal NSAIDs, causing right heart overload, hydrops, or fetal death.
Presbyopia
Presbyopia is the age-related loss of the eye's accommodative focusing power, causing blurred near vision from about age 40-45. Treated with reading glasses, multifocal contacts, miotic eye drops (pilocarpine, aceclidine/VIZZ), or surgery.
Prestin
Prestin (SLC26A5) is the motor protein of cochlear outer hair cells, driving voltage-dependent electromotility for cochlear amplification. Named from Italian 'presto'; its anion transport, voltage sensing, and 2021 structures distinguish it from other SLC26 transporters.
Presumed ocular histoplasmosis syndrome
Presumed ocular histoplasmosis syndrome (POHS), also called ocular histoplasmosis syndrome, is a retinal condition linked to prior Histoplasma capsulatum exposure, marked by histo spots, peripapillary atrophy, absent vitritis, and choroidal neovascularization causing vision loss.
PREVENT-DX study
PREVENT-DX (NCT04344704) is a Spanish-led, randomized, open-label multicenter study of 462 patients comparing a single-chamber ICD with a DX floating atrial dipole and SMART algorithm against conventional single-chamber discrimination for preventing inappropriate therapies and MACCE over 24 months.
Primary color
Primary color: the defining colors of a color model, additive RGB for light, subtractive CMY for inks, traditional RYB; grounded in Young-Helmholtz trichromacy, Maxwell's work, and CIE standards like BT.2020 and D65.
Primary intestinal lymphangiectasia
Primary intestinal lymphangiectasia (Waldmann's disease, PIL) is a rare disorder of dilated intestinal lacteals causing protein-losing enteropathy, edema, and lymphopenia, treated mainly with a low-fat MCT diet.
Primary lateral sclerosis
Primary lateral sclerosis (PLS) is a rare, sporadic neurodegenerative disorder of adult upper motor neurons causing slowly progressive spasticity, distinct from ALS by pure UMN involvement, 2020 consensus criteria, and much longer survival.
Primary motor cortex
Primary motor cortex (M1), Brodmann area 4, in the precentral gyrus; the cortical output area for voluntary movement. Contains Betz cells, somatotopic motor homunculus (Penfield and Boldrey, 1937), corticospinal and corticobulbar tracts, contralateral control.
Primary open-angle glaucoma
Primary open-angle glaucoma (POAG), also called chronic open-angle glaucoma, is a chronic progressive optic neuropathy with an open anterior chamber angle. About 53 million cases in 2020; elevated IOP is the only modifiable risk factor, and treatment lowers IOP with drops, SLT laser, or surgery.