Variant ataxia telangiectasia

Case contributed by Danielle Byrne

Presentation

55 year old male presented with acute right sided weakness and headache. Past medical history included long-standing generalised dystonia including retrocollis with progressive upper and lower limb dystonia. On examination, he had poor balance and mobility, his head was turned back and to the left and he had difficulty with pronunciation. Scleral telangiectasia were noted.

Patient Data

Age: 55 years
Gender: Male
MRI

Axial T2

1.4cm ovoid mixed T2 hypo/hyper-intense focus in the periventricular white matter of the left frontal lobe.

Diffuse bilateral T2 hyperintense signal in the deep and periventricular white matter of the cerebral hemispheres.

Axial FLAIR

1.4cm ovoid mixed FLAIR hypo/hyper-intense focus in the periventricular white matter of the left frontal lobe.

Diffuse bilateral FLAIR hyperintense signal in the deep and periventricular white matter of the cerebral hemispheres.

Axial DWI B1000

1.4cm focus of high signal in the periventricular white matter of the left frontal lobe consistent with abnormal restricted diffusion and suspicious for an acute infarct or intraparenchymal haematoma.

Axial ADC Map

ADC map confirms a focus of abnormal restricted diffusion in the periventricular white matter of the left frontal lobe, suspicious for an acute infarct or intraparenchymal haematoma.

Axial T1WI

T1 hyperintense focus in the periventricular white matter of the left frontal lobe which correlates to the previously identified focus of abnormal restricted diffusion and mixed T2/FLAIR hyper/hypo-intense signal constant with an acute intraparenchymal haematoma.

Axial SWI

SWI demonstrates diffuse bilateral hypointensities consistent with microhaemorrhages in the periventricular and deep white matter of the cerebral and cerebellar hemispheres, with relative sparing of the juxtacortical white matter and brainstem. The acute left frontal intraparenchymal haematoma is also identified.

Sagittal T2WI

Sagittal T2 weighted images demonstrate pronounced atrophy of the cerebellum, most marked in the vermis. Again noted is an ovoid mixed T2 hypo/hyper-intense focus in the periventricular white matter of the left frontal lobe and diffuse bilateral T2 hyperintense signal in the deep and periventricular white matter of the cerebral hemispheres.

Photo

Figure 1. Western blot analysis of a lymphoblastic cell line from the patient's blood (column 11) demonstrates a greatly reduced level of ATM protein consistent with Ataxia Telangiectasia. Column 2 demonstrates complete absence of ATM protein in a patient with classic AT.

AOA2 (ataxia oculomotor apraxia type 2).

Figure 2. Patient's blood was exposed to 1 Gray of gamma rays. Chromosomal radiosensitivity of the T lymphocytes was exposed. There were 26 cells with 21 bits of damage compared with 8 bits of damage in the normal control in 50 cells consistent with a moderate increase in chromosomal radiosensitivity. In classic AT, a 5-10 fold increased level of gamma ray induced chromosome damage is expected.

Case Discussion

Ataxia telengiectasia (AT) is a rare autosomal recessive neurodegenerative multisystem disorder caused by two truncating ATM gene mutations leading to total loss of ATM kinase activity and, therefore, function of the ATM protein 1. In less severe cases, termed AT variants, there is retention of some ATM kinase activity due to either expression of very low levels of normal ATM protein (from splice site mutations) or expression of mutant ATM (from missense mutations) 2.

AT variants are a phenotypically heterogeneous group, characterised by slower progression of clinical signs, an extended lifespan compared to most patients with the classical form of the disease with less cellular sensitivity to radiation, susceptibility to malignancies and recurrent sinopulmonary infection.

In the absence of clinical history, this case demonstrates a radiologic diagnostic conundrum. The most striking abnormality is the presence of diffuse bilateral microhaemorrhages with a superimposed acute intraparenchymal haematoma and cerebral amyloid angiopathy would be high on the list of differentials. However, the presence of extensive bilateral T2/FlAIR hyperintense signal within the white matter seems disproportionate to the degree of likely concomitant small vessel disease. Given that this is a case of an adult brain, the diagnosis of AT may elude the radiologist as patients with the classic form of AT usually do not survive beyond childhood. The presence of diffuse white matter T2/FLAIR signal abnormality and disproportionate cerebellar atrophy clinches the diagnosis of variant ataxic telangiectasia.

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Case information

rID: 50830
Case created: 23rd Jan 2017
Last edited: 31st Oct 2017
Inclusion in quiz mode: Included

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