Radiology Abstract Lhermitte-Duclos disease (LDD) is a rare cerebellar lesion of uncertain ori- gin. It is linked to an autosomal- dom- inant phakomatosis known as Cowden’s disease in 40% of patients. The MRI features of LDD are almost unique and can be considered diag- nostic. We report on a patient who presented with the typical MRI fea- tures of the above disease, and discuss the imaging features, pathology and genetics. Introduction Lhermitte-Duclos disease (LDD) or dysplastic gangliocytoma is a rare slow-growing benign lesion of the cerebellum. Only 150 cases have been reported.1 Its precise aetiology is uncertain. It is postulated that this disease may be a hamartoma, a devel- opmental anomaly, a manifestation of a phakomatosis or a low-grade neo- plasm. Recent published data suggest that LDD is a hamartomatous lesion related to a phakomatosis, rather than a neoplasm.2 LDD is often asymptomatic in early life, but usually becomes clinical- ly apparent in the third and fourth decades. Reported cases have present- ed from birth to 74 years old.1 There is no gender bias. The clinical manifesta- tions are usually related to posterior fossa mass-effect and resultant sec- ondary obstructive hydrocephalus. The most frequent complaints are headaches and ataxia due to intracra- nial hypertension. This occurs in 70% of patients. Cerebellar signs and symptoms are present in 40 - 50%. One-third of patients have associated cranial nerve palsies and long tract dysfunction. Visual problems, neck stiffness, vertigo and subarachnoid haemorrhage are less commonly noted presenting features.1 Case A 62-year-old male patient pre- sented in a delirious state to the casu- alty department. He had complained of severe headaches for the 4 days prior to his admission. There was no associated nausea and vomiting or obvious gait disturbance. On exami- nation no papilloedema was noted. In view of his symptoms, a computed tomography (CT) scan (Siemens Somatom Sensation 16, Erlangen, Germany) of the brain was per- formed. CT revealed a large hypo dense lesion involving the posterior aspect of the right cerebellar hemi- sphere and the vermis (Fig. 1). It had a geographic shape, was well-defined, with no calcification. Compression and distortion of the 4th ventricle with consequent supratentorial hydrocephalus was noted. Magnetic resonance imaging (MRI) (1,5T Siemens Symphony Maestro, Erlangen, Germany) revealed a well-marginated infratentorial mass in the right cerebellar hemisphere. Preservation and enlargement of the gyral pattern was noted (Figs 2 and 3). No enhancement was seen after admin- istration of intravenous contrast. Discussion The definitive diagnosis of LDD is histopathological, but MR imaging can preoperatively characterise the disease sufficiently well. The abnor- mality seen in LDD is related to abnormal development of the cere- bellar cortex. Usually, the normal cere- bellar cortex consists of an inner gran- 30 SA JOURNAL OF RADIOLOGY • February 2005 CASE REPORT CT and MRI find- ings in Lhermitte- Duclos disease M R H Bayat MB ChB (UCT), Dip PEC (SA) J Sarawan MB BCh (Wits), FCR (SA) Department of Radiology Nelson R Mandela School of Medicine University of KwaZulu-Natal Durban Fig. 1. Contrast-enhanced CT scan demonstrates a large non-enhancing intra-axial mass in the right cerebellum with a large temporal horn of left later- al ventricle. Radiology 2/24/05 4:50 PM Page 30 CASE REPORT 31 SA JOURNAL OF RADIOLOGY • February 2005 ular layer, an outer molecular layer and an intervening Purkinje cell layer. In LDD there are abnormal ganglion cells in the granular layer, thickening and hypermyelination of the molecu- lar layer and loss of the middle Purkinje cell bodies.3 On CT, LDD is usually seen as a well-defined isodense- to hypodense mass in the posterior cranial fossa with no contrast enhancement. Alternating bands of density that are usually seen on MRI may be seen on high-resolution fine-slice CT through the posterior fossa. Calcifications may be present. Depending on the size, mass effect with displacement of the 4th ventricle and obstructive hydro- cephalus may be present The histopathology of LDD forms the basis of the MRI findings. The demonstration of the typically striated, laminated or ‘tiger-striped’ appearance involving the cerebellar tissue is unique. Focal or diffuse cerebellar engorgement with prominent cerebel- lar folia and mass-effect are noted. This is caused by the close apposition of thickened cerebellar folia that have lost their secondary arborisation, resulting in alternating bands of tissue intensi- ties. The atrophic white matter, the adjacent layers of abnormal ganglionic neurons and the innermost part of the molecular layers have prolonged signal (hypointense on T1 and hyperintense on T2 and FLAIR). The outer part of the molecular layer of adjacent folia and the intervening leptomeningeal space are iso-intense to normal cerebel- lar tissue both on T1 and T2 sequences. Lack of MR contrast enhancement is emphasised as an important MR diag- nostic criterion of the disease but according to Spaargaren et al.3 contrast enhancement has been reported. This is postulated to be due to venous pro- liferation that may also explain the large draining veins that are seen on angiography and as flow voids on MRI. LDD is the only lesion besides cere- bellar infarction that respects the nor- mal cerebellar convolution markings despite causing enlargement. It is the abovementioned features together with the history that are pathogno- monic. The only other lesion that may produce similar findings is cerebellar infarction, but the clinical presentation is usually very different. MRI is excellent in defining the limits of the lesion to accomplish the most radical excision during surgery. There is an association between Lhermitte-Duclos and Cowden’s dis- ease. This association has been noted in 40% of cases.4 Cowden’s disease is an autosomal-dominant condition with a prevalence of 1 in 200 000. It is due to a mutation of the PTEN gene that is located on chromosome 10q 22-23. This gene is related to tumour suppres- sion. Mutation promotes proliferation and invasion of cells and failure of nor- mal apoptosis. Cowden’s disease is characterised by multiple hamartomas and neoplasms affecting the skin, thy- roid, breast, and genitourinary and gas- trointestinal tracts. The skin lesions are present in 90% of patients. The muco- cutaneous manifestations form the pathognomonic basis for diagnosing Cowden’s disease and consist of the fol- lowing features: trichilemmomas, acral keratoses, as well as mucinous fibromas and oral papillomas.1,4 Despite the benign nature, surgical excision is the treatment of choice, although some centres may prefer con- servative management in asympto- matic cases. Wide excision is necessary due to the risk of recurrence. However this is difficult because of ill-defined macroscopic margins. Radiation thera- py is ineffective. References 1. Perez-Nunez A, Lagares A, Benitez J, et al. Lhermitte-Duclos disease and Cowden disease: clinical and genetic study in five patients with Lhermitte-Duclos disease and literature review. Acta Neurochir 2004; 146: 679-690. 2. Buhl R, Barth H, Hugo H-H, Straube T, Mehdorn HM. Dysplastic gangliocytoma of the cerebellum: Rare differential diagnosis in space occupying lesions of the posterior fossa. Acta Neurochir 2003; 145: 509-512. 3. Spaargaren L, Cras P, Bomhof MAM, et al. Contrast enhancement in Lhermitte-Duclos dis- ease of the cerebellum: correlation of imaging with neuropathology in two cases. Neuroradiology 2003; 45: 381-385. 4. Nagaraja S, Powell T, Griffiths PD, Wilkinson ID. MR imaging and spectroscopy in Lhermitte- Duclos disease. Neuroradiology 2004; 46: 355- 358. Fig. 2. Contrast-enhanced parasagittal coronal T1- weighted image reveals a hypo-intense mass with bands isodense to normal cerebellar tissue. A prominent vein is also noted draining into the straight sinus. Fig. 3. Axial T2-weighted image shows the classic findings of a right hemi-cerebellar lesion with lam- inated hypertrophic folia and alternating curvilinear bands of high and low signal intensity. Similar find- ings were noted on the fluid attenuated inversion recovery (FLAIR) images. Radiology 2/24/05 4:50 PM Page 31