1,527 articles
Sadhana Jackson
Sadhana Jackson is an American pediatric neuro-oncologist at NIH's NINDS who studies drug delivery across the blood-brain barrier and received a 2025 Presidential Early Career Award.
Sandhoff disease
Sandhoff disease (GM2 gangliosidosis type II, O variant) is a rare autosomal recessive lysosomal storage disorder caused by HEXB variants, deficient hexosaminidase A and B, GM2 ganglioside accumulation, and infantile, juvenile, and adult forms.
Sandifer syndrome
Sandifer syndrome: rare GERD complication in infants and young children causing paroxysmal dystonic neck, back, and head posturing that mimics seizures; resolves with antireflux treatment.
Sanfilippo syndrome
Sanfilippo syndrome (mucopolysaccharidosis type III, MPS III) is an autosomal recessive lysosomal storage disorder with four subtypes (SGSH, NAGLU, HGSNAT, GNS) causing heparan sulfate accumulation, childhood neurodegeneration, and, since 2025, the first FDA-approved gene therapy, Fayuvi.
Savant syndrome
Savant syndrome, also called autistic savant skills, is a rare condition in which an 'island of genius' contrasts with overall disability; about one in 10 autistic people have savant abilities, in domains like music, art, and calendar calculating.
Scalp dysaesthesia
Scalp dysaesthesia (scalp dysesthesia), a chronic neurocutaneous condition of scalp itching, burning, and pain without skin findings; diagnosis of exclusion linked to cervical spine disease, psychiatric comorbidity, and neuropathic mechanisms.
Schaaf-Yang syndrome
Schaaf-Yang syndrome (SYS, Chitayat-Hall syndrome, OMIM 615547) is a rare imprinted-gene neurodevelopmental disorder caused by truncating variants in the paternal MAGEL2 allele at 15q11.2, marked by neonatal hypotonia, joint contractures, intellectual disability, and autism, overlapping but distinct from Prader-Willi syndrome.
Schilder disease
Schilder disease, or myelinoclastic diffuse sclerosis, is a rare progressive CNS demyelinating disorder of childhood (onset 5-14 years), a multiple sclerosis variant with fewer than 20 reported sporadic cases, predominantly male, often mimicking brain tumor or abscess.
Schizencephaly
Schizencephaly is a rare congenital brain malformation with gray matter-lined clefts running from ventricle to cortex, classified as closed-lip or open-lip, causing epilepsy, motor deficits, and variable intellectual disability; prevalence about 1.48 per 100,000 births.
Schnyder corneal dystrophy
Schnyder corneal dystrophy (SCD), formerly Schnyder crystalline corneal dystrophy, is a rare autosomal dominant stromal corneal dystrophy caused by UBIAD1 mutations on 1p36, with cholesterol and phospholipid corneal deposits, crystals in only about half of patients, and hypercholesterolemia association.
Scintillating scotoma
Scintillating scotoma, also called fortification spectrum or teichopsia, is the most common migraine visual aura: a flickering, jagged-edged blind spot spreading C-shaped over 5–60 minutes, linked to cortical spreading depression.
Scleral staphyloma
Scleral staphyloma (ICD-11 9B52), also called scleral ectasia, is a circumscribed outpouching of the thinned eye wall with uveal protrusion; posterior staphyloma is a hallmark of pathologic myopia, classified by Curtin into ten types.
Scleritis
Scleritis, inflammation of the sclera of the eye, is a painful, vision-threatening disorder with anterior (9 of 10 cases), necrotizing, and posterior subtypes, often linked to rheumatoid arthritis and other systemic disease.
Scotoma
Scotoma: an area of absolute or partial vision loss within the visual field. Types include central, paracentral, arcuate, and scintillating scotomas; causes include glaucoma, macular disease, optic neuropathy, and migraine; mapped by perimetry and the Amsler grid.
Secondary angle closure glaucoma
Secondary angle closure glaucoma: angle closure from an identifiable underlying disease (neovascularization, uveitis, ICE syndrome, tumors, aqueous misdirection, lens or drug causes) raising IOP and damaging the optic nerve, unlike primary pupillary-block angle closure.
Secondary childhood glaucoma
Secondary childhood glaucoma (ICD-11 9C61.42) is pediatric glaucoma from an underlying ocular anomaly, systemic disease, acquired condition, or cataract surgery; CGRN classification divides it into four subtypes, managed mainly with medications and tube shunts.
Secondary Chorea
Secondary chorea (ICD-11 8A01.1) is involuntary choreiform movement caused by acquired conditions, infections, drugs, metabolic, autoimmune, vascular, or paraneoplastic disorders, unlike genetic primary chorea; treatment targets the underlying cause.
Secondary dystonia
Secondary dystonia (ICD-11 8A02.1) is dystonia caused by another condition or external factor such as drugs, stroke, trauma, hypoxia, toxins, or heredodegenerative disease, distinguished from primary dystonia by rest-onset movements, hemidystonia, and other neurological signs.
Secondary headache
Secondary headache (ICD-11 8A84) is headache attributed to another causative disorder, spanning ICHD-3 categories 5-12 (trauma, vascular, infection, substances, and others). Distinguished from primary headache by red flags such as thunderclap onset, papilledema, and fever.
Secondary intracranial hypotension
Secondary intracranial hypotension (ICD-11 8D61.1) is low CSF pressure, usually below 60 mm H2O, caused by an identified dural injury such as lumbar puncture, spinal or cranial surgery, shunt placement, or trauma, causing orthostatic headache.
Secondary open-angle glaucoma
Secondary open-angle glaucoma: optic neuropathy with an open drainage angle caused by identifiable conditions such as pseudoexfoliation, pigment dispersion, neovascularization, trauma, inflammation, drugs, or lens-induced mechanisms, treated by lowering IOP plus addressing the cause.
Secondary parkinsonism
Secondary parkinsonism (ICD-11 8A00.2) is parkinsonism caused by drugs, vascular disease, toxins, infection, trauma, or hydrocephalus rather than Parkinson disease; drug-induced parkinsonism is the most common cause and is often reversible.
Secondary progressive multiple sclerosis
Secondary progressive multiple sclerosis (SPMS) is the MS stage following relapsing-remitting MS, marked by relapse-independent disability accrual (PIRA). About 50% of RRMS patients transition within 20 years; diagnosis is retrospective, and siponimod treats active SPMS.
Secondary syringomyelia
Secondary syringomyelia (ORPHA:99857, ICD-10 G95.0) is a rare spinal cord disease: a syrinx forms secondary to blocked CSF flow, cord injury, dysraphism, or intramedullary tumors, causing dissociated sensory loss.
Secondary tremor
Secondary tremor (ICD-11 8A04.3) is tremor caused by an identifiable underlying disorder, lesion, drug, or toxin, such as metabolic disturbances, cerebellar lesions, Holmes tremor, or drug-induced tremor, unlike primary tremor syndromes.
Segmental myoclonus
Segmental myoclonus (ICD-11 8A06.1) is rhythmic myoclonus limited to one or contiguous spinal or brainstem segments, typically 1–3 Hz with 50–500 ms EMG bursts, no EEG correlate, caused by local lesions, and often refractory to clonazepam and botulinum toxin.
Seizure
Seizure: transient episode of abnormal synchronous electrical brain activity lasting seconds to minutes. Classified by ILAE 2017 as focal, generalized, or unknown onset; epilepsy requires two or more unprovoked seizures.
Self-limited epilepsy with autonomic seizures
Self-limited epilepsy with autonomic seizures (SeLEAS), formerly Panayiotopoulos syndrome, is a childhood epilepsy in which seizures begin with vomiting, pallor, and eye deviation, then remit within 1 to 2 years.
Self-limited epilepsy with centrotemporal spikes
Self-limited epilepsy with centrotemporal spikes, formerly benign rolandic epilepsy or BECTS, is the most common focal epilepsy of childhood, causing brief facial seizures that stop by puberty.
Self-limited infantile epilepsy
Self-limited infantile epilepsy (SeLIE), formerly benign familial infantile seizures, a genetic epilepsy with brief focal seizure clusters from 3 to 20 months, mainly PRRT2-related, resolving spontaneously.