Nervous and sensory conditions

Allergic contact blepharoconjunctivitis

Allergic contact blepharoconjunctivitis, also called contact blepharoconjunctivitis, is a delayed hypersensitivity reaction of the eyelid skin and conjunctiva, typically triggered by cosmetics, metals, or eye drops.

Allodynia

Allodynia, also called touch-evoked pain, is pain from a stimulus that does not normally provoke pain, defined by the IASP. Distinct from hyperalgesia, it arises through peripheral and central sensitization in neuropathic pain, fibromyalgia, and migraine.

Alternating skew deviation

Alternating skew deviation is a supranuclear vertical eye misalignment that reverses with gaze direction, affecting about 12% of skew deviation patients, usually from pretectal, cerebellar, or cervicomedullary lesions.

Amaurosis fugax

Amaurosis fugax (transient monocular blindness) is brief, painless one-eye vision loss from retinal ischemia, usually carotid emboli; carries about half the stroke risk of cerebral TIA.

Amelocerebrohypohidrotic syndrome

Amelocerebrohypohidrotic syndrome, or Kohlschütter-Tönz syndrome (OMIM 226750), is a rare autosomal recessive disorder combining amelogenesis imperfecta, infantile epilepsy, and intellectual decline, caused mainly by ROGDI and sometimes SLC13A5 mutations.

Amnesia

Amnesia is partial or total loss of the ability to recall past experiences or store new memories, classified as retrograde, anterograde, or sense-specific. Causes include brain injury, stroke, Wernicke-Korsakoff syndrome, encephalitis, dementias, and dissociative trauma; transient global amnesia is the most common acute form.

Amyotrophic lateral sclerosis-Plus

Amyotrophic lateral sclerosis-Plus (ALS-Plus, ICD-11 8B60.5) is ALS with superimposed extrapyramidal, cerebellar, autonomic, oculomotor, or cognitive dysfunction; about 13.6% of a 550-patient cohort, with shorter survival and more pathogenic mutations than classic ALS.

Anacusis

Anacusis (anakusis, anacusia) is total deafness, complete absence of auditory perception in one or both ears; ICD-11 code MB40.2, defined as hearing loss above 120 dB by some sources.

Anaesthesia of skin

Anaesthesia of skin (ICD-11 MB40.3; ICD-10 R20.0) is partial or complete loss of skin sensation, usually circumscribed, from sensory nerve damage such as injury or leprosy.

Anaplastic ependymoma

Anaplastic ependymoma, formerly WHO grade III ependymoma, a rare malignant glial tumor of the brain or spinal cord; term retired in WHO CNS5 2021, treated with surgery plus radiotherapy, worse prognosis than grade II.

Anaplastic ganglioglioma

Anaplastic ganglioglioma (AGG), a former WHO grade III mixed neuronal-glial CNS tumor diagnosis, removed by the 2021 WHO CNS5 classification because molecular testing showed most cases are other tumor types such as pleomorphic xanthoastrocytoma or glioblastoma, IDH-wildtype.

Anaplastic oligoastrocytoma, dual genotype

Anaplastic oligoastrocytoma, dual genotype (ORPHA:251663, ICD-11 2A00.0Y) is a rare IDH-mutant mixed glioma carrying both astrocytic (ATRX/TP53) and oligodendroglial (1p/19q codeletion) markers, retained as a WHO NEC category.

Anarthria

Anarthria (loss of articulate speech) is the complete inability to articulate speech, the most severe form of dysarthria, with comprehension preserved; caused by stroke, ALS, or brainstem injury, ICD-11 code MA80.20.

ANE syndrome

ANE syndrome (alopecia, neurologic defects, and endocrinopathy syndrome, ANES) is a rare autosomal recessive ribosomopathy caused by biallelic RBM28 mutations, distinct from acute necrotizing encephalopathy, causing alopecia, intellectual disability, motor decline, and pituitary hormone deficiency.

Aniridia

Aniridia, also called congenital aniridia or PAX6-related aniridia, is a rare panocular disorder from PAX6 haploinsufficiency at 11p13, causing iris hypoplasia plus keratopathy, glaucoma, cataract, and foveal hypoplasia, sometimes with WAGR syndrome.

Aniridia-cerebellar ataxia-intellectual disability syndrome

Aniridia-cerebellar ataxia-intellectual disability syndrome, or Gillespie syndrome (OMIM 206700), is a rare ITPR1-related disorder with partial bilateral aniridia, fixed dilated scalloped pupils, non-progressive cerebellar ataxia, hypotonia, and mild to moderate intellectual disability, first described in 1965.

Aniseikonia

Aniseikonia (also ocular image size inequality) is a binocular vision condition where the two eyes perceive images of different size or shape, from optical causes like anisometropia or retinal causes like epiretinal membrane; symptoms begin around 1-3%.

Anisometropia

Anisometropia: significant interocular difference in refractive error, usually SER ≥1.00 D. Causes amblyopia, reduced stereopsis, aniseikonia; contact lenses preferred correction; increasingly linked to myopia.

Anomic aphasia

Anomic aphasia, also called nominal or amnesic aphasia, is the mildest fluent aphasia syndrome: marked word-retrieval failure with preserved fluency, comprehension, and repetition, linked to left perisylvian lesions, stroke, and Alzheimer disease.

Anophthalmic socket

Anophthalmic socket (ICD-11 9A25.0): the orbit remaining after eye removal or congenital absence, managed with orbital implants (PMMA, silicone, hydroxyapatite), prostheses, and reconstruction for contracture, exposure, and motility problems.

Anosmia

Anosmia is complete loss of the sense of smell, distinct from hyposmia and parosmia. Key facts: olfactory training helps about 26% of patients, head trauma causes anosmia in 4-16% of TBI cases, and smell loss predicts 5- and 10-year mortality.

Anosognosia

Anosognosia, from Greek 'without disease knowledge', is unawareness of one's own neurological or psychiatric deficits. Coined by Babinski in 1914 for hemiplegia denial; common in stroke, dementia, schizophrenia (50–90%), and bipolar disorder (40%).

Anterior cerebral artery syndrome

Anterior cerebral artery syndrome: stroke deficits from infarction in ACA territory, also called ACA infarction syndrome. Rare (0.3–4.4% of strokes), cardioembolic in origin, with leg-predominant weakness, abulia, alien hand, and akinetic mutism.

Anterior cutaneous nerve entrapment syndrome

Anterior cutaneous nerve entrapment syndrome (ACNES), also called abdominal cutaneous nerve entrapment syndrome or intercostal neuralgia, is entrapment of T7-T12 intercostal nerve branches at the rectus abdominis border, causing chronic localized abdominal wall pain diagnosed by Carnett test and treated with injections or neurectomy.

Anterior ischemic optic neuropathy

Anterior ischemic optic neuropathy (AION), also called NAION or AAION, is sudden infarction of the optic nerve head from posterior ciliary artery occlusion; the nonarteritic form is the most common acute optic neuropathy over age 50, while the arteritic form signals giant cell arteritis and is a steroid emergency.

Anterograde amnesia

Anterograde amnesia: inability to form new long-term memories after brain injury or disease, sparing working and implicit memory. Famous case H.M. (1953 medial temporal lobectomy); common causes include Alzheimer's disease, TBI, anoxia, Korsakoff syndrome.

Anthony P. Adamis

Anthony P. Adamis is an American ophthalmologist who co-discovered VEGF's role in blinding eye disease and led development of the first anti-VEGF drug for wet AMD.

Anti-NMDA receptor encephalitis

Anti-NMDA receptor encephalitis (anti-NMDAR encephalitis) is the most common autoimmune encephalitis, caused by IgG antibodies against the GluN1/NR1 NMDA receptor subunit, often triggered by ovarian teratoma, diagnosed by CSF antibodies, and treated with immunotherapy and tumor removal.

Aphasia

Aphasia, also known as dysphasia, is a language disorder caused by damage to the brain's language areas, usually on the left side, most often from stroke.