Sunday, 11 September 2011

Hypomelanosis of Ito MRI

A 15 y o male with scholastic backwardness, Autism. No neurological signs.
MRI Brain Axial T2w, FLAIR, Diffusion and T2*GRE.
Axial T2 and FLAIR images show multiple enlarged peri vascular spaces in bilateral fronto parietal peri ventricular white matter with surrounding patches of Gliosis.

Imagingwise: Hypomelanosis of Ito (HMI) ……I feel.

Hypomelanosis of Ito 

HMI, formerly also called Incontinentia Pigmenti Achromians.

Clinically characterized by unilateral or bilateral hypopigmented whorls, streaks, and patches.
The abnormal skin pigmentation follows Blaschko lines on the back, whorls on the abdomen and linear stripes on the limbs. Zones of hypomelanosis are easily seen in patients with a darker skin.
In eyes may see, hypopigmented areas in the iris and the retina. Corneal opacities, macrophthalmia, microphthalmia, strabismus, epicanthal folds, choroidal atrophy, and optic nerve hypoplasia may be seen.
Abnormalities in hair color, alopecia, hypertrichosis, and trichorrhexia may be observed.
Fingernails may be abnormal.
Numerous types of dental dysplasia may be present.
Macrocephaly is relatively common; microcephaly is less frequent.
The face may be asymmetrical.

Neurological impairment can be quite severe with hemi megalencephaly or neuronal migrational defects, leading to intractable seizures and serious mental and motor handicap. About 80% of the patients have mental retardation, which varies from mild to profound Autism.

Imaging findings:
Even MRI of the brain may be normal.
Some may have major CNS abnormalities, including neuronal migrational abnormalities like cortical dysplasia or heterotopias.
Diffuse cerebral atrophy, cerebellar hypoplasia
Vascular abnormalities.
The common and relatively minor abnormalities consist of multifocal and confluent patches suggestive of Gliosis  and focal myelination defects in periventricular and deep white matter with increased peri vascular spaces.

Reference: Magnetic resonance of myelination and myelin disorders:  Marjo S. van der Knaap, J. Valk, Frederik Barkhof : Chapter 55.

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