Wednesday, 3 August 2011

Wilson disease MRI

A 29 yo female under psychiatric treatment for hyper activity and easy irritability, ataxic gait, dysarthria and tremors. 
KF ring in eyes on clinical examination. 
Usg abdomen normal.

MRI Brain
Axial FLAIR images shows bilateral symmetric T2 hyper intensity involving caudate nuclei, putamen, thalami, peri aqueductal grey matter and tegmentum of mid brain supportive to clinical diagnosis of Wilson’s disease. Mild focal parenchymal swelling with faint foci of high signals on diffusion attributed to prolonged T2 effect.

Wilson Disease

Syn: Hepatolenticular degeneration.
An inborn error of copper metabolism characterized by Liver cirrhosis, Kayser - Fleischer ring of cornea, softening and degeneration of Basal ganglia.

Imaging wise best diagnostic clue is bilateral symmetric T2 hyper intensity in basal ganglia and thalami. Focal parenchymal swelling noted in initial stages of disease followed by atrophy. 

Location wise most commonly involves putamina (with predilection for outer rim), Pons (dorsal and central region) > followed by Caudate, Globus pallidi, Thalami (ventro lateral nuclei) > Mid brain, Cerebellum (vermis and dentate nuclei) > Dentato rubro thalamic, Ponto cerebellar and cortico spinal tracts > Cortical and sub cortical white matter. 

CT is often normal. May find atrophy in later stage of disease. Copper deposition in basal ganglia does not increase density on CT. Even contrast enhanced CT going to be non contributory. 
MRI the investigation of choice.
On T1w images, signals usually reduced. Occasionally increase in signal noted in affected basal ganglia due to para magnetic effect of deposited copper. Increased signal in Globus pallidi if there is an associated porto systemic encephalopathy, a hepatic component of WD. 
On T2 and FLAIR images, hyper, hypo as well as mixed signals are known. Hyper intensity is more common than hypo intensity. Hypo intensity is possible due to increase in Iron content in affected deep grey nuclei. 
A characteristic ‘ Face of Giant panda’ sign , is described on axial Flair and T2w sections at the level of mid brain, occur due to hyper intensity in the region of tegmentum with low signal in red nuclei, normal signals of pars reticulata of substantia nigra.
Dw images provide data on histo pathological stages of WD in a given case. In acute stages of disease immediately after onset of neurological symptoms a high signal may be noted on diffusion in the affected areas. The signal intensity reduces on subsequent imaging. However an increase in signal can be noted again in later stages of disease if there is an associated necrosis, spongiform degeneration and demyelination in the affected nuclei. 
Post contrast MRI is non contributory, not needed for diagnosis. 
MR Spectroscopy may show reduced NAA / Creatinine ratio, reduced Choline / Creatinine ratio, Reduced Myoinositol in cases of porto systemic shunting. 

Imaging wise DDs
Leigh disease.
CO poisoning.
Creutzfeldt Jakob disease. 
Japaneses Encephalitis.

Clinical presentation
Most common signs and symptoms
- Neurologic : Asymmetric tremor, ataxia, dyskinesia, dysarthria, dystonia mainly face, incoordination, parkinsonian like symptoms.
- Psychiatric : Hyperkinetic behavior, irritability, emotional liability, difficulty in concentration, depression, psychosis, mania, personality change.
- Acute hepatitis, Kayser Fleischer ring in cornea. 
- Subtle pyraminal signs in up to 20% of cases. 

40- 50% present with liver disease. 35-50% with neurological and psychiatric symptoms. 
KF Rings always present in neurologic WD.

Age and Gender
Often recognized in 2nd to 3rd decade. 
M = F; but for fulminant WD with liver failure, encephalopathy and coagulopathy is more common in females with ratio of 1:4. 
Onset of liver disease usually at the age of 8-16 yrs. 
Hepatic form of WD is most common presentation in children where as Neuro psychiatric symptoms are common in older individuals. Neurological symptoms are rare before 12 yrs.
Once symptomatic WD is fatal if untreated. 
Fulminant WD has mortality of 70%. 

Penicilline, Trientine, Zinc, NH4 tetr thiomolybdate.
Liver transplant for severe hepatic decompensation. 

Reference: Diagnostic imaging Osborn.

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