1,527 articles
Multiple mitochondrial dysfunctions syndrome type 5
Multiple mitochondrial dysfunctions syndrome type 5 (MMDS5), or ISCA1 deficiency, is a rare autosomal recessive mitochondrial disease causing seizures, spasticity, and neurologic decline, usually fatal in early childhood.
Multiple open wounds of head
Multiple open wounds of head: ICD-11 code NA01.7 (ICD-10-CM S01.7), a leaf code under NA01 Open wound of head for more than one open head wound, with postcoordination and cluster coding rules.
Multiple sclerosis
Multiple sclerosis (MS, sclérose en plaques), chronic autoimmune demyelinating disease of brain and spinal cord; over 3 million affected, relapsing and progressive forms, treated with disease-modifying therapies.
Multiple system atrophy
Multiple system atrophy (MSA), historically known as Shy-Drager syndrome or striatonigral degeneration, is a rare progressive neurodegenerative disease of adults combining parkinsonism, ataxia, and autonomic failure.
Muscle Denervation
Muscle denervation is the loss or removal of a muscle's nerve supply (MeSH D009121), causing atrophy, fibrillation, and altered membrane properties; diagnosed by needle EMG and treated with electrical stimulation, nerve transfer, or targeted muscle reinnervation.
Muscle tension dysphonia
Muscle tension dysphonia (MTD), primary or secondary, is a functional voice disorder from excessive paralaryngeal muscle tension causing hoarseness and vocal fatigue; treated mainly with voice therapy.
Mutism
Muteness (mutism): inability to produce oral-verbal expression despite normal comprehension, seen in brain disease (frontal lobe, cerebellar, akinetic mutism), psychosis, and selective mutism, an anxiety disorder.
Myasthenia gravis
Myasthenia gravis is a chronic autoimmune neuromuscular disease causing fatigable weakness, first described by Thomas Willis in 1672, treated with anticholinesterases, thymectomy, immunosuppressants, and newer targeted biologics like efgartigimod and nipocalimab.
Myelitis
Myelitis is inflammation of the spinal cord, most often discussed as transverse myelitis. Causes include MS, NMOSD, MOGAD, infections, and idiopathic cases; diagnosed by MRI, CSF, and antibody tests.
Myelomeningocele with hydrocephalus
Myelomeningocele with hydrocephalus (ICD-11 LA02.00) is an open spinal neural tube defect combined with ventricular CSF accumulation. Hydrocephalus affects 15–25% of MMC babies; prenatal repair (MOMS trial) roughly halves shunt placement rates versus postnatal repair.
Myeloschisis
Myeloschisis (ORPHA:645398) is a severe open neural tube defect with a flat, exposed neural placode lacking a sac, always with Chiari II malformation; distinct from myelomeningocele, with different fetal surgery outcomes.
Myoclonic disorders
Myoclonic disorders are a group of movement disorders defined by myoclonus, sudden brief shock-like muscle jerks from contraction or sudden inhibition, coded 8A06 in ICD-11.
Myoclonic epilepsy of infancy
Myoclonic epilepsy of infancy (MEI, formerly benign myoclonic epilepsy in infancy) is a rare self-limited epilepsy with myoclonic seizures starting between 4 months and 3 years in normal infants, remitting within 6 months to 5 years.
Myoclonus
Myoclonus: brief, shock-like involuntary muscle jerks (10–50 ms), positive or negative (asterixis). Classified as physiological, essential, epileptic, symptomatic, or psychogenic; cortical, subcortical, spinal, or peripheral by generator; diagnosed with video-EEG/polygraphy.
Myoclonus-dystonia syndrome
Myoclonus-dystonia syndrome (MDS, DYT11) is a rare genetic movement disorder combining lightning-like myoclonus with mild to moderate dystonia, childhood onset, mainly SGCE mutations with maternal imprinting, alcohol-responsive myoclonus, and pallidal DBS for refractory cases.
Myotonia fluctuans
Myotonia fluctuans, also called exercise-induced delayed-onset myotonia, is a rare autosomal dominant SCN4A (Nav1.4) sodium channel myotonia with fluctuating stiffness after exercise and potassium ingestion, no weakness or cold sensitivity.
Myotonia permanens
Myotonia permanens, a severe persistent form of potassium-aggravated myotonia, is an autosomal dominant SCN4A (Nav1.4) sodium channelopathy with childhood-onset continuous myotonia, respiratory risk, and the G1306E variant frequent in Chile.
Myxopapillary ependymoma
Myxopapillary ependymoma (MPE), ICD-O 9394/1, is a CNS WHO grade 2 ependymoma of the conus medullaris, cauda equina, and filum terminale in adults, with over 90% long-term survival and recurrence reduced by gross-total resection.
Naegleriasis
Naegleriasis, or primary amebic meningoencephalitis (PAM), is a rare, nearly always fatal brain infection caused by Naegleria fowleri, the brain-eating ameba, acquired when contaminated warm freshwater enters the nose; fewer than 10 US cases yearly, 167 cases 1962-2024 with four survivors.
Narcolepsy
Narcolepsy, a chronic sleep-wake disorder affecting about 1 in 2,000 people, caused by loss of hypothalamic orexin (hypocretin) neurons; symptoms include excessive daytime sleepiness and cataplexy; oveporexton (Orzeyful) approved 2026.
Narcolepsy type 2
Narcolepsy type 2 (narcolepsy without cataplexy) is a central disorder of hypersomnolence with excessive daytime sleepiness, MSLT latency ≤8 min and ≥2 SOREMPs, no cataplexy, and no reliable biomarker; orexin deficiency reclassifies it as type 1.
NARP syndrome
NARP syndrome (neuropathy, ataxia, retinitis pigmentosa) is a rare maternally inherited mitochondrial disorder caused by MT-ATP6 mutations, most often m.8993T>G at 70-90% heteroplasmy, causing neuropathy, ataxia, retinopathy, and seizures, treated supportively.
Nasal step
Nasal step, a glaucomatous visual field defect first described by Rönne in 1909: a sensitivity difference above and below the nasal horizontal midline, a nerve fiber bundle defect that begins as a scotoma.
Nasolacrimal duct cyst
Nasolacrimal duct cyst (dacryocystocele, dacryocele): congenital cyst of the tear drainage duct, presenting at birth as a bluish medial canthal mass, causing tearing, dacryocystitis, and nasal obstruction; managed first conservatively, then surgically.
Nasolacrimal duct obstruction
Nasolacrimal duct obstruction (blocked tear duct) is blockage of tear drainage from eye to nose, congenital (valve of Hasner, resolves spontaneously in ~90% of infants) or acquired (inflammation, trauma, tumors), treated by massage, probing, intubation, or dacryocystorhinostomy.
Nasopalpebral lipoma-coloboma syndrome
Nasopalpebral lipoma-coloboma syndrome (NPLCS, OMIM 167730) is an extremely rare autosomal dominant congenital syndrome with eyelid and nasopalpebral lipomas, bilateral eyelid colobomas, telecanthus, and maxillary hypoplasia.
Nasu-Hakola disease
Nasu-Hakola disease (PLOSL), a rare autosomal recessive leukodystrophy from TYROBP or TREM2 mutations, causing bone cysts, fractures, and presenile dementia, mostly in Japanese and Finnish populations.
Nathalie syndrome
Nathalie syndrome, also known as deafness-cataract-skeletal anomalies syndrome, is a rare genetic disorder combining hearing loss, cataracts, spinal muscular atrophy, and potentially fatal heart disease.
NDE1-related microhydranencephaly
NDE1-related microhydranencephaly (MHAC, OMIM 605013) is an autosomal recessive disorder from biallelic NDE1 variants, causing extreme microcephaly, absent cerebral hemispheres, ventricular dilation, and severe disability.
Near vision impairment
Near vision impairment (ICD-11 9D90.7) is presenting near visual acuity worse than N6 at 40 cm with existing correction, mainly from presbyopia; 826 million people are unaddressed, over 800 million lack reading glasses, and WHO targets a 40-point eREC rise by 2030.