Patient is in chronic renal failure and on dialysis. Presented with seizures.
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Bilateral FLAIR hyperintense putamina are noted. The medial, lateral and posterior aspects of the putamina are delineated by the hyperintense edematous external capsules. This imaging appearance constitutes the "lentiform fork sign"
A focal area of right posterior cortical hyperintensity is noted.
The globus pallidus appears engulfed by T2 hyperintensity which represents the edematous medullary laminae, which divide the lentiform nucleus into three masses. T2 hyperintensity is seen extending down into the midbrain and the mesial temporal lobes. Corresponding hypointense changes in the internal and external capsules are seen.
No evidence of restricted diffusion is seen, however characteristically elevated ADC signal is seen involving the internal and external capsules.
The subcortical gray matter is known to be exquisitely sensitive to a range of toxins and metabolic disturbances 1. Uremic encephalopathy (UE) is an acquired toxic syndrome related to kidney dysfunction. Whereas the literature concerning encephalopathy associated with liver disease is rich and multifaceted, there are very few studies dealing with this aspect of renal failure, thus little is known of the pathophysiology of UE. The complexity of normal kidney function, however, makes it likely that renal failure leads to a variety of abnormalities that exert synergistic deleterious effects on the brain 2. Metabolic acidosis has been proposed as a possible mechanism for UE, which is associated with the lentiform fork sign on MRI 3.
- 1. Albin RL. Basal ganglia neurotoxins. Neurol Clin. 2000;18 (3): 665-80. Pubmed citation
- 2. Daroff RB, Fenichel GM, Jankovic J et-al. Bradley's Neurology in Clinical Practice: Expert Consult - Online and Print, 6e. Saunders. ISBN:1437704344. Read it at Google Books - Find it at Amazon
- 3. Kumar G, Goyal MK. Lentiform Fork sign: a unique MRI picture. Is metabolic acidosis responsible?. Clin Neurol Neurosurg. 2010;112 (9): 805-12. doi:10.1016/j.clineuro.2010.06.006 - Pubmed citation