Episodic ataxia (EA) is an autosomal dominant disorder characterized by sporadic bouts of ataxia (severe discoordination) with or without myokymia (continuous muscle movement). There are seven types recognized but the majority are due to two recognized entities. Ataxia can be provoked by psychological stress or startle, or heavy exertion, including exercise. Symptoms can first appear in infancy. There are at least six loci for EA, of which 4 are known genes. Some patients with EA also have migraine or progressive cerebellar degenerative disorders, symptomatic of either familial hemiplegic migraine or spinocerebellar ataxia. Some patients respond to acetazolamide though others do not. Signs and symptoms
Typically, episodic ataxia presents as bouts of ataxia induced by startle, stress, or exertion. Some patients also have continuous tremors of various motor groups, known as myokymia. Other patients have nystagmus, vertigo, tinnitus, diplopia or seizures. Cause
The various symptoms of EA are caused by dysfunction of differing areas. Ataxia, the most common symptom, is due to misfiring of Purkinje cells in the cerebellum. This is either due to direct malfunction of these cells, such as in EA2, or improper regulation of these cells, such as in EA1. Seizures are likely due to altered firing of hippocampal neurons (KCNA1 null mice have seizures for this reason). Pathophysiology
EA1: KCNA1
Type 1 episodic ataxia (EA1) is characterized by attacks of generalized ataxia induced by emotion or stress, with myokymia both during and between attacks. This disorder is also known as episodic ataxia with myokymia (EAM), hereditary paroxysmal ataxia with neuromyotonia and Isaacs-Mertens syndrome.
Band keratopathy is a corneal disease derived from the appearance of calcium on the central cornea. This is an example of metastatic calcification, which by definition, occurs in the presence of hypercalcemia. Signs and symptoms
Signs and symptoms of band keratopathy include eye pain and decreased visual acuity. Causes
Band keratopathy has several causes. These causes include uveitis, interstitial keratitis, superficial keratitis, phthisis, sarcoidosis, trauma, intraocular silicone oil, systemic diseases (high levels of calcium in the blood, vitamin D intoxication, Fanconis Syndrome, low levels of phosphorus in the blood, gout, milk-alkali syndrome, myotonic dystrophy, and chronic mercury exposure). Pathology
Band keratopathy is seen when there is calcification of the epithelial basement membrane, Bowmans membrane, and the anterior stroma with destruction of Bowmans membrane. The calcium salts are intracellular when the process is due to alteration of systemic calcium metabolism, whereas they are extracellular when due to local disease. Diagnosis
Band keratopathy is diagnosed by slit lamp examination of the eye. Treatment
Treatment is indicated if vision is threatened or if the eye is uncomfortable. It is important to recognize and treat any underlying condition. Improvement of vision may be obtained by scraping off the opacity. Topical disodium EDTA can be used as a chelating agent. It can also be removed with the excimer laser (phototherapeutic keratectomy). Other modalities include diamond burr and lamellar keratoplasty. References


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