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|Year : 2019 | Volume
| Issue : 5 | Page : 1396-1397
Tadpole Brain Atrophy in Adult-Onset Alexander Disease
V Abdul Gafoor, Joe James, James Jose, B Smita
Department of Neurology, Government Medical College, Kozhikode, Kerala, India
|Date of Web Publication||19-Nov-2019|
Dr. Joe James
Department of Neurology, Government Medical College, Kozhikode - 673 008, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gafoor V A, James J, Jose J, Smita B. Tadpole Brain Atrophy in Adult-Onset Alexander Disease. Neurol India 2019;67:1396-7
A 57-year-old male presented with chronic progressive neurological symptoms of a two year duration characterized by difficulty walking, clumsiness of hands, and slurring of speech. On examination, he had bilateral gaze evoked horizontal and down-beating nystagmus and wasted tongue with fasciculations. His extremities were spastic and deep tendon reflexes were hyperactive with bilateral extensor plantar response with bilateral cerebellar signs and a wide-based ataxic gait, with intact sensations.
Magnetic resonance imaging (MRI) of the brain showed tadpole-like atrophy of the brainstem, as a result of a marked thinning of the medulla oblongata, cervical spinal cord, and midbrain tegmentum with preserved pontine base [Figure 1]. Based on the clinical and MRI findings, a diagnosis of adult-onset Alexander disease (AOAD) was considered. The glial fibrillary acidic protein (GFAP) gene sequencing showed a novel heterogeneous missense variation in exon 6 of the GFAP gene (chr17:42988659C>T; Depth 123×) that results in an amino acid substitution of threonine for alanine at codon 358 (p. Ala 358Thr; ENT00000586793) confirming the clinical diagnosis.
|Figure 1: (a) Sagittal T1-weighted magnetic resonance image showing “tadpole” atrophy of brainstem; i.e., atrophy of medulla oblongata and cervical cord (arrowhead) with preserved basis pontis (arrow). (b) Axial T2 sequence showing marked atrophy of medulla oblongata (arrows)|
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Alexander disease (AD) is a leukodystrophy that is pathologically characterized by the presence of Rosenthal fibers. The underlying genetic defect is mutations in the GFAP gene. The disease is traditionally classified as infantile (onset before 2 years of age), juvenile (onset between 2 and 12 years of age), and adult (onset after 12 years of age) according to the age of onset. But subsequently AD was divided into two groups: type I was characterized by early onset, seizures, megalencephaly, and typical MRI features, and type II with a later age at onset characterized by brainstem features and atypical MRI findings.
Progressive atrophy of the medulla oblongata and upper cervical spinal cord leading to a tadpole pattern, with hyperintensities on T2-weighted images, is highly suggestive of AOAD or type II AD. Involvement of the hilum of the dentate nucleus with less involvement of the cerebellar white matter is frequent. In patients younger than 40 years, supratentorial periventricular abnormalities in signal intensity and spotty areas of postcontrast enhancement are observed, which are rarely seen in older patients.
Awareness of this characteristic imaging pattern helps in the identification of patients to be submitted to genetic testing for the GFAP gene. Diagnosis may be considered even in asymptomatic patients examined with imaging for unrelated reasons and implies proper genetic counseling to families.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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