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Radiologically selective visual pathway involvement in adult onset cerebral adrenoleukodystrophy
  1. D S FARRELL,
  2. M C LAWDEN
  1. Department of Neurology, Leicester Royal Infirmary, Leicester, UK
  2. Department of Radiology
  1. Dr M C Lawden, Leicester Royal Infirmary, Leicester, LE1 5WW, UK
  1. N MESSIOS
  1. Department of Neurology, Leicester Royal Infirmary, Leicester, UK
  2. Department of Radiology
  1. Dr M C Lawden, Leicester Royal Infirmary, Leicester, LE1 5WW, UK

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A case of adult onset cerebral adrenoleukodystrophy is presented with serial MRI showing selective involvement of the visual system with spread of disease along the fibre tracts of this system.

Adult onset cerebral adrenoleukodystrophy is the rarest presentation of adrenoleukodystrophy.1 2 It may present with various symptoms often including visual impairment.3 Brain MRI may show multiple areas of symmetric high signal intensity within cerebral white matter, usually affecting the occipital lobes.4-6We present a case of adrenoleukodystrophy, in whom serial MRI demonstrated selective progression of demyelination through the visual pathways.

A thirty year old man presented in May 1996 with a 7 month history of deteriorating vision, slurred speech, incoordination, poor balance, generalised weakness, sleep disturbance, and headaches. His symptoms were worse on the right. He had no symptoms of postural hypotension.

Brain MRI at four different times spanning 2 years. (A) May 1996: T2 weighted axial. (B) May 1996: contrast enhanced T1 weighted axial. (C) October 1996: T2 weighted axial. (D) October 1996: T1 weighted contrast enhanced axial. (E) October 1996: T1 weighted contrast-enhanced axial. (F) August 1997: T2 weighted axial. (G) August 1997: T1 weighted contrast enhanced coronal. (H) May 1998: T2 weighted axial. (I) May 1998: T1 weighted contrast enhanced coronal.

His mother had been shown to be a carrier of X linked adrenoleukodystrophy (XL-ALD). His two elder brothers had died of XL-ALD at the ages of 6 and 7 years. In 1993 our patient had been shown to have abnormal serum concentrations of very long chain fatty acids (VLCFAs) and to be a carrier of the XL-ALD gene. At that time he was asymptomatic and had no abnormal neurological signs. Crohn's disease had been diagnosed in 1987 after an ileal resection although this had remained in remission.

On examination, visual acuities were 6/12 (right), 6/9 (left). Fields were full to confrontation using a finger but there was a left homonymous field defect to a red pin and he had a left afferent pupillary defect. Fundoscopy showed bilateral optic atrophy. The remainder of the cranial nerve examination was normal. In the arms tone and power were normal, but coordination was mildly impaired on the right. The reflexes were exaggerated and Hoffman's sign was present bilaterally. A palmomental reflex was present on the right. In the legs power was normal, but tone was increased and there were several beats of ankle clonus; reflexes were exaggerated and plantar responses were upgoing. Coordination was impaired in both legs, his gait was ataxic, and Romberg's test was positive. He had a minor reduction in vibration sensation at the right ankle; otherwise sensation was normal. He appeared moderately tanned, but there was no other hyperpigmentation. Supine blood pressure was 114/78, falling to 108/80 on standing. The remainder of the examination was normal.

Routine biochemistry was normal. A morning cortisol was 469 nmol/l (normal >160 nmol/l), but a short synacthen test showed an abnormally flat response (serum cortisol rise from 338 to 449 nmol/l over 1 hour). His plasma VLCFA profile was abnormal consistent with XL-ALD. Humphrey visual field testing demonstrated a left homonymous field defect. Brain MRI was abnormal (figure A and B). He was placed on a very low fat diet with supplements of glycerol trioleate oil.

By October 1996 his headaches had settled but his eyesight, memory, coordination, and walking were worse. Visual acuity was below 6/60 in both eyes. Brain MRI was repeated (figure C-E). By August 1997 there had been no new clinical developments (MRI figure F-G). In May 1998 he complained of navigational difficulties in familiar surroundings, further memory loss, and cognitive decline (MRI figure H-I).

In May 1996 (figure A) T2 weighted axial imaging showed high signal intensity areas in the region of the right lateral geniculate nucleus and left optic tract. The occipital white matter was normal. T1 weighted images with gadolinium contrast enhancement (figure B) showed bilateral enhancement of the intracerebral optic tracts.

By October 1996 (figure C) T2 weighted axial imaging showed spread of the areas of high signal intensity continuously from the lateral geniculate nuclei posteriorly along the optic radiations into the white matter of both occipital lobes, more prominent on the right. T1 weighted images showed contrast enhancement in the optic chiasm and optic tracts (figure D), lateral geniculate nuclei, origins of the optic radiations, and right occipital white matter (figure E).

By August 1997 (figure F) there had been further progression in the white matter changes in both occipital lobes, with spread to the splenium of the corpus callosum. Contrast enhancement (figure G) was seen in the optic radiations and right occipital white matter. The cerebellar white matter was of low signal intensity, with a small area of contrast enhancement above the fourth ventricle to the right of the midline.

In May 1998 (figure H and I) the changes in white matter were yet more extensive with the appearance of ring enhancement.

Our case illustrates MRI appearances typical of adrenoleukodystrophy and demonstrates in particular the evolution of these changes with time. The tendency of this condition to affect the visual pathways selectively is well illustrated as is the spread of disease along the fibre tracts of that system. This allowed visualisation of parts of the visual system, the anatomy of which is usually hidden—for example, the intracerebral portion of the optic tracts. The characteristic MRI appearances are thought to result from an advancing front of active demyelination, followed by an area of inflammatory cellular response demonstrating contrast enhancement, surrounded by areas of established damage, gliosis, and neuronal loss.7

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