Friday 3 August 2012

Radiation induced Cryptic Vascular malformation

A 50 yo male operated for right parietal Glioma with post operative radiotherapy.
Clinically started worsening after 5th week. 
The follow up CT with MRI FLAIR and T2*GRE.
Cryptic Vascular malformation
Non Contrast CT study of brain shows multiple punctuate hyperdense foci are the Radiation induced Cryptic Vascular Malformation
Axial T2*GRE images show  multiple punctuate low signal intensity foci "blooming" related to blood degradation products are the Radiation induced Cryptic Vascular Malformations predominantly the Capillary Telangiectasia
Axial FLAIR image show bilateral confluent peri ventricular T2 white matter hyper intensities suggestive of Radiation induced Leukoencephalopathy 
Radiation induced brain injury

Spectrum of insult includes edema, arteritis, leukoencephalopathy, mineralizing microangiopathy, necrotizing leukoencephalopathy, radiation-induced tumors and Cryptic Vascular Malformations.

Depending up on the time of presentation divided into acute, early delayed injury and late delayed injury:
Acute injury: 1-6 weeks after or during treatment ; Mild and reversible, vasogenic edema.
Early delayed injury: 3 weeks to several months; Edema & demyelination.
Late delayed injury: Months to years after treatment; More severe, irreversible.

Imaging findings:
Radiation injury: Mild focal hypodense / T2 hyper intense vasogenic edema to areas of necrosis.
Radiation necrosis: Irregular enhancing lesion, single or multiple.
Leukoencephalopathy:  Bilateral confluent white matter hypodensity / T2 hyperintensity predominantly involve peri ventricular white matter, sub cortical U fibers involves late.
Mineralizing microangiopathy: Bilateral basal ganglia and sub cortical white matter faint calcification best seen on CT. An associated cerebral cortical atrophy.
Necrotizing leukoencephalopathy:  Areas of white matter necrosis.
Cryptic Vascular Malformation: Best seen on MRI T2* GRE as punctate low signal intensity foci represent capillary Telangiectasia.

Pathological Basis:
Radiation-induced neurotoxicity : Direct radiation induced Glial and WM damage. Sensitivity of oligodendrocytes is more than neurons to radiation induced damage. Effects on fibrinolytic system and immune effects.
Radiation-induced vascular injury: Altered vascular permeability, endothelial and basement membrane damage, accelerated atherosclerosis, telangiectasia and cavernoma formation.
Radiation-induced tumor like sarcoma seen after ~ 5 years, genetic predisposition.

Distinguishing residual/recurrent neoplasm from Radiation induced Necrosis difficult using morphology alone. MRS, PET or SPECT may help delineate recurrent tumour from radiation necrosis.

Reference: DI Anne G Osborn. 

1 comment:

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