Steroid responsive encephalitis in dogs

We found reports of 251 patients (median age 52years [range 18-86], 73% females, 80 [32%] with preexisting thyroiditis). Patients presented encephalitis signs with convulsions (n=117; 47%), confusion (n=115, 46%), speech disorder (n=91, 37%), memory impairment (n=107, 43%), gait disturbance (n=67, 27%) and persecutory delusions (n=61, 25%). Twenty-eight patients (11%) presented progressive memory impairment and 26 (10%) isolated psychiatric disorders. In serum, 34% of patients were positive for anti-thyroid peroxidase (TPO) antibodies, 7% for anti-thyroglobulin (TG) antibodies, and 69% both. Thyroid-stimulating hormone levels were usually normal, at 2 UI/ml [-205]. Cerebrospinal fluid from 10/53 patients (19%) was positive for anti-TPO antibodies, 2/53 (4%) anti-TG antibodies and 28 (53%) both. Electroencephalography findings were abnormal for 82% of patients, showing diffuse slowing consistent with encephalopathy (70%) or epileptic activity (14%). The first-line treatment was steroids in 193 patients and other immunosuppressive drugs in 10 cases. At a median follow-up of 12months [range -110], 91% of patients showed complete or partial neurological response, with anti-TPO and -TG antibody titers at 347 UI/ml [0-825,000] and 110 UI/ml [0-50,892], respectively. During follow-up, 40 patients (16%) experienced at least one relapse. Relapse was more frequent in patients with initial coma (26% vs 13%, p=).

Because steroids are lipophilic, they diffuse easily through the cell membranes, and therefore have a very large distribution volume. In their target tissues, steroids are concentrated by an uptake mechanism which relies on their binding to intracellular proteins (or " receptors ", see below). High concentration of steroids are also found in adipose tissue, although this is not a target for hormone action. In the human male, adipose tissue contains aromatase activity, and seems to be the main source of androgen-derived estrogens found in the circulation. But most of the peripheral metabolism occurs in the liver and to some extent in the kidneys, which are the major sites of hormone inactivation and elimination, or catabolism (see below).

Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.

Steroid responsive encephalitis in dogs

steroid responsive encephalitis in dogs


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