Fibrolipomatous Hamartoma! Rare condition with pathognomonic radiological findings and a frequent flyer on certifying exams. Also known as neural fibrolipoma, lipofibromatous hamartoma, perineural lipoma and intraneural lipoma. FH is a benign lesion that results from abnormal fibrofatty tissue growth which leads to infiltration of the endoneurium, perineurium and epineurium. The infiltration leads to fusiform enlargement of the affected nerve. FH primarily affects the median nerve (80% of cases) followed by the ulnar, radial and brachial plexus nerves. In MRI, a fusiform fat containing lesion is seen within the carpal tunnel and displacing the surrounding structures. The enlarged fatty median nerve shows internal thickened nerve bundles which give the “coaxial cable-like” appearance on axial images and the “spaghetti string” appearance on coronal images. Because of the fat content of the lesion, fat suppression is seen on the T2 and T1 fat suppressed images. The lesion does not enhance. It’s good to remember that FH is highly associated to Macrodystrophia Lipomatosa. Treatment consists of nerve decompression and debulking and reconstruction when associated to Macrodystrophia Lipomatosa.
