| Description |
Isolated ateriovenous malformations (AVMs) of the retina are rare (743,744) (Fig. 38.76). They were first described by Magnus in 1874 and were regarded for many ears as a simple ophthalmologic curiosity. In 1930, however, Yates and Paine described an extensive vascular malformation in for A-T represent nearly1% of the population (733). In one study, the risk for cancer was 3.8 for men and 3.5 for women (729). Breast cancer in women was especially prevalent in this study, whose authors also found that occupational or diagnostic exposure to radiation increased its risk. Abnormal carbohydrate metabolism sometimes appears during the teenage years in patients with A-T. Blood sugars and insulin levels are high, whereas the presence of glucose in the urine is low (734). Hypogonadism and stunted growth are also prevalent. Because of the increased sensitivity of patients with A-T to ionizing irradiation, MR imaging is the diagnostic procedure of choice for patients suspected of having this disease. The earliest atrophic changes occur in the lateral cerebellum and superior vermis (735). This progresses to diffuse cerebellar atrophy, especially affecting the vermis and superior cerebellar cortex (735,736), with the cisterna magna and 4th ventricle being correspondingly enlarged (737). A diffuse white-matter hyperintensity by MR imaging, resulting in a mistaken diagnosis of a leukodystrophy, was noted in one patient with subsequent typical features of ataxia-telangectasia (738). In addition to A-T, the differential diagnosis of patients presenting with cerebellar ataxia and ocular dysmotility includes spinocerebellar ataxia type 2, Friedreich's ataxia, and ataxia with ocular apraxia (739,740). Spinocerebellar ataxia type 2 is an adult-onset, autosomal-dominant disorder, whereas Friedreich's ataxia and ataxia with ocular apraxia are autosomal-recessive. Friedreich's ataxia is distinguished by the prominent peripheral neuropathy and ocular motility disturbance more characterized by fixation instability of square-wave jerks (741). Ataxia with ocular apraxia has a similar ocular motility disturbance to that of A-T but is not associated with choreoathetosis, oculocutaneous telangiectasia, immune dysfunction, chromosomal instability, hypersensitivity to x-rays, and a high incidence of respiratoryinfections and neoplasias (739)-findings that are the hallmarks of A-T. The treatment of patients with A-T is directed at its complications. Antibiotics and -globulins are used to prevent and treat infections. Tumor therapy is problematic because of the increased sensitivity of these patients to radiation therapy and chemotherapy. Consequently, prognosis for a long life is poor. Families should be advised of the 25% chance of having another child with the same condition. Because the parents and other heterozygote carriers of the gene for A-T have an increased risk of cancer, particularly breast cancer in women (729,742), these heterozygote carriers should undergo periodic examinations for possible cancer, especially mammography in women. the ipsilateral cerebral hemisphere and retina of a patient who died from an intracerebral hemorrhage. Subsequently, Brock and Dyke (745) and Bonnet and colleagues (746) stressed the relationship between retinal and intracranial AVMs (Figs. 38.77). |
