A Radiological Curiosity of a Rare Diagnosis: Lhermitte-Duclos Disease

Imaging Findings

On a CT examination, dysplastic cerebellar gangliocytoma presents as a low-density cerebellar mass, which may contain calcification and does not show enhancement.⁸ MRI is the best imaging performed to diagnose Lhermitte–Duclos disease (LDD). The MRI protocol is standard: axial, sagittal, and coronal planes are required. The most common sequences are T1, T2, Flair, DWI (b1000), the Injection of Gadolinium and spectroscopy at 135m/s, MRI checks for architectural disorganization and cortical hypertrophy, and loss of parallelism of the cerebellar lamellae or folia.³

The characteristic of tiger striped and flaky appearance is found in T2 FSE and T2 Flair in the form of leafy and tabby mass syndrome of the cerebellar hemisphere. The involvement is often unilateral, very rarely bilateral, only one case reported in literature.⁹ In T1-weighted image, there is distortion of foliar architecture of cerebellum in isointense or hypointense compared with gray substance (Figs. 1 and 5). T2 Flair, T2-weighted axial, and coronal imaging revealed a well-circumscribed hyperintense mass with lamellar areas of isointensity which occurs as a result of enlargement of cerebellar folia and compressed sulci (Fig. 2). After injection of gadolinium (T1FS + Gado), two figures can be observed: either a hypervascularization compared with the healthy contralateral parenchyma, a situation which is very rare, in connection with venous abnormalities of development and not an angiogenesis or an absence of contrast enhancement which proves that post-gadolinium-enhanced axial T1-weighted image demonstrates no significant enhancement within the mass testifying to the integrity of the blood–brain barrier (Fig. 4).^10,11 In diffusion it is identified by a global hyperintensity of the lesional zone with an alternation of the zones in restriction of diffusion and absence of restriction of diffusion confirmed by the ADC cartography(Fig. 3). Diffusion properties in LDD can be variable depending on the contributions from the inner layer and the thick outer molecular layer with large dysplastic neurons.¹² This testifies to hypercellularity and the high intralesional axonal concentration.¹³

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Fig. 5 Right cerebellum hemisphere normal in T1-weighted sequence MRI.

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Spectroscopy sequence shows a non-specific drop in NAA with inverted lactate peak and reduction in choline. An absence of an increase in choline leading to a drop in the NAA/Cr and Cho/Cr ratio, reflects the absence of aggressiveness of a tumor in the majority of cases.^12,14 Mass syndrome has a mass effect most often on the fourth ventricle and sometimes on the protuberance. This increase in the cerebellar mass ratio is related to an abundance of dilated intra- and perilesional veins, in the altered cell layers and along the leptomeninges. The abnormality is hemispheric and unilateral most often but only one case of bilaterality has been reported.^9,15 In sum, the typical striated or tiger-striped folia pattern is a characteristic finding of LDD also named dysplastic gangliocytoma.¹⁶

The radiologist must be careful with the medulloblastoma which can mimic this diagnosis by rarely showing a resemblance of these morphological characteristics except that in the latter we observe a peak of choline on spectroscopy.^13,14 From the above, histological proof is inescapable. Histological hallmarks of the disease are thickening and hypermyelination of the outer molecular layer, loss of Purkinje cells and white matter, dysplastic ganglion cells with rounded nuclei, and abundant mitochondria invading the inner granular layer.^2,5

Recurrences are possible in case of incomplete excision and a syndromic association with Cowden disease is frequently found involving LDD, multiple skin lesions, and cancers (breast, thyroid, digestive, and genitourinary). In this Cowden disease, LDD represents the neurological expression of this rare genetic disease.^17,18

Diagnosis criteria of Cowden Syndrome adapted from MESTER 2014¹⁸

According to literature, in few cases, LDD could be associated with other malformation of the posterior fossa like Chiari malformation.⁴ Association with other lesions such as macrocephaly, polydactylies, multiple hemangioma, goiter, intestinal polyps was often observed.¹⁹ Diagnostic considerations or differential included glioma, subacute infarct, vascular malformation with cerebellar venous congestion, rhombencephalosynapsis, cerebellar dysplasia, medulloblastoma or, less likely, cerebellitis^8,10

Current modes of treatment described in the literature consisted of medical (medications or radiotherapy) or surgical treatment, comprising of VP shunt or biopsy and lesion debulking^4,20