1,240 articles
Pituitary abscess
Pituitary abscess: a rare pus collection in the pituitary gland or sella turcica, under 1% of pituitary lesions; primary or secondary; headache and visual loss; treated by transsphenoidal drainage plus antibiotics.
Placentophagy
Placentophagy, or placentophagia, is the eating of a human placenta after childbirth, most often as capsules, a practice that grew since the 1970s despite controlled research finding no evidence of its claimed benefits.
Plagiocephaly
Plagiocephaly, or flat head syndrome, is asymmetric infant skull flattening. Deformational (positional) plagiocephaly affects 5-48% of newborns; synostotic plagiocephaly from premature suture fusion is rare. Treatment ranges from repositioning to helmet therapy.
Plantar reflex
Plantar reflex: sole-of-foot reflex; normal adults flex the big toe, while upgoing toe (Babinski sign, described 1896) indicates corticospinal tract dysfunction; insensitive but highly specific.
Polyphasic sleep
Polyphasic sleep: distributing sleep into 3+ episodes per 24 h (Uberman, Everyman, Dymaxion schedules) to cut total sleep. Controlled studies show impaired vigilance, reduced deep sleep, and adverse health effects versus monophasic sleep.
Polysomnography
Polysomnography (PSG), the overnight sleep study, records EEG, EOG, EMG, breathing, oxygen, and heart activity to diagnose sleep apnea, narcolepsy, and parasomnias; term coined 1974.
Polyvagal theory
Polyvagal theory, proposed by Stephen Porges in 1995, links vagal brainstem nuclei to social behavior and autonomic states; its physiological and evolutionary premises are contested by Grossman and other experts.
Post anoxic brain damage
Post anoxic brain damage (ICD-11 8E44) is encephalopathy from circulatory arrest, hypotension, or asphyxia, also called hypoxic-ischemic brain injury; marked by coma after cardiac arrest, multimodal prognostication at 72 hours, and slow rehabilitation recovery.
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-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 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.
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.
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.
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.
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 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.
Primary tethered cord syndrome
Primary tethered cord syndrome (primary tethered spinal cord syndrome), a congenital low-lying, traction-fixed spinal cord with thickened filum terminale, causing progressive neurologic, musculoskeletal, and bladder/bowel symptoms; treated by surgical detethering.
Primitive reflexes
Primitive reflexes: involuntary brainstem-mediated motor responses (Moro, grasp, rooting, Galant, tonic neck) present from about 25 weeks of gestation, normally inhibited by 4-6 months, and clinically significant when absent, persistent, or reemergent.
Progressive bulbar palsy
Progressive bulbar palsy (PBP), also called progressive bulbar atrophy, is a motor neuron disease/ALS phenotype affecting lower brain stem cranial nerves, causing dysarthria, dysphagia, tongue and facial weakness, and fasciculations, usually progressing to widespread ALS.
Progressive muscular atrophy
Progressive muscular atrophy (PMA), also called the lower motor neuron variant of ALS, is a rare sporadic adult-onset motor neuron disease with pure LMN signs, slower course, TDP-43 pathology, and 22% later UMN conversion.
Progressive outer retinal necrosis
Progressive outer retinal necrosis (PORN), also called rapidly progressive herpetic retinal necrosis, is a VZV-caused viral retinitis of severely immunocompromised patients, mainly advanced AIDS, marked by minimal inflammation, rapid bilateral "cracked mud" retinal lesions, and poor vision outcomes.