A rare case of relapsing seizures in a young adult

A 26-year-old man, with a history of recurrent seizures despite therapy with levetiracetam 500 mg bid, presented to our hospital for alternating headaches, with associated vertiginous episodes.

MRI indicated a mass in the left cerebellar hemisphere of the posterior fossa (axial dimension of 44 mm). The lesion exhibited no substantial restriction of diffusion, and only the posterior portion of the mass showed a slight improvement after gadolinium delivery. It resulted in herniated cerebellar tonsils 14 mm below the McRae line, causing a mass effect. Syringobulbia is also visible, with a prominent extension on the right side. There is a small rise in rCBV inside the improved component. The spectroscopic analysis revealed a slight decrease in Cho and NAA and the preservation of Cr and Lac peaks. The patient underwent osteo-dural decompression of the posterior cerebral fossa and partial excision of a cerebellar lesion on the left side. The pathological examination confirmed Lhermitte-Duclos disease (LDD).

Dysplastic cerebellar gangliocytoma is an uncommon benign tumour of the cerebellum composed of dysplastic ganglion cells. Also referred to as Lhermitte-Duclos disease (LDD). LDD often affects the worm or cerebellar hemisphere and is frequently infratentorial. As it grows, the characteristic symptom of LDD is a tumour-like mass that replaces the normal architecture of the cerebellum. It is unknown if the dysplastic cerebellar gangliocytoma (LDD) is malignant or atypical [1]. LDD may be associated with Cowden syndrome (CS), a disorder characterised by numerous hamartomas. Owing to the intimate relationship between LDD and CS, imaging of other organ systems, such as the breast and colon, should be investigated in LDD patients to exclude occult tumours in other organs [3]. LDD may affect anybody, however, the majority of sufferers are between 20 and 40 years old. Individuals with intracranial hypertension may exhibit no symptoms or may appear with headaches, nausea, and vomiting. Paralysis of the cranial nerves and visual problems are also frequent. LSD evolves gradually over decades [3]. LDD is treated by monitoring and treating the individual's symptoms, unless the mass effect symptoms are severe enough to warrant surgery. On NECT, LDD lesions are often hypodense. Calcification is uncommon. In general, CECT demonstrates little to no improvement. The [4]  T1WI MRI reveals hypointense linear bands. T2WI displays the pathogenic pattern of alternating interior hyperintense LDD and outer hypointense in larger cerebellar folia, indicating restricted diffusion and cellular origin [5]. MRI spectroscopy reveals normal or slightly diminished Cho:Cr ratios and normal NAA concentrations. A lactate doublet is seen [5].

Learning points

• Dysplastic cerebellar gangliocytoma, also known as Lhermitte-Duclos disease, is a rare hamartomatous lesion of the cerebellum that primarily affects young people.
• It is considered diagnostic to have a non-enhancing mass in the posterior fossa that is hypointense on T1 and hyperintense on T2-weighted imaging with parallel linear striations, giving the cerebellum a "tigroid" appearance.