Paraneoplastic Cerebellar Syndrome Presented as Cerebellar Hypermetabolism in a Patient With Occult Breast Carcinoma.

ABSTRACT: A 47-year-old woman presented with an acute cerebellar syndrome. Neither cerebellar atrophy nor an infarction or tumor was shown on MRI. A diagnostic CT demonstrated enlarged axillary lymph nodes, but no primary tumor. Puncture of these nodes showed non-small cell carcinoma. 18F-FDG PET/CT imaging was performed and suggested an occult breast carcinoma, which was confirmed by pathological examination. It also showed cerebellar hypermetabolism, consistent with a PCS (paraneoplastic cerebellar syndrome). This case shows that 18F-FDG PET imaging may be of value in patients in which a PCS is considered clinically, particularly in patients suspicious for an occult malignancy.

This 18F-FDG PET/CT scan (coronal, sagittal, and transversal 18F-FDG PET/CT images; upper panel, PET images; lower panel, low-dose CT images) was acquired in a 47-year-old woman who presented with an acute cerebellar syndrome. She had progressive symptoms of vertigo, diplopia, nausea, and an unstable gait. Neurological examination revealed dysarthria, third-degree nystagmus to the left, downbeat nystagmus when looking down, ataxia of the right limb, and an unstable broad basic gait.

No cerebellar atrophy, infarction, tumor, diffusion restrictions, or signal changes were shown on MRI (left panel, transversal fluid-attenuated inversion recovery image at the level of the cerebellum; right panel, transversal diffusion-weighted image at the same level). A diagnostic CT of the thorax and abdomen (not shown) demonstrated enlarged axillary lymph nodes, but no primary tumor. Puncture of these nodes showed non–small cell carcinoma. In combination with the clinical signs, a paraneoplastic syndrome induced by an occult breast or lung cancer was considered, and consequently, 18F-FDG PET/CT imaging was performed from the skull extending to the groin. The PET/CT scan suggested an occult breast carcinoma (not shown), which was confirmed by pathological examination. It also showed cerebellar hypermetabolism (see Figure), consistent with a paraneoplastic cerebellar syndrome (PCS). Finally, anti-Yo antibodies were detected, which are related to the presence of breast cancer.[1] At first, the patient was treated with methylprednisolone for 5 consecutive days, with improvement of symptoms. Second, when the symptoms increased a few days later, a 5-day IV immunoglobulin treatment was started. Finally, the patient received a combination of pertuzumab, trastuzumab, paclitaxel, and carboplatine followed by surgery, as a therapy for breast carcinoma. Unfortunately, after 3 months, neurological examination showed no improvement compared with the patient's first admission. Clinically, an acute cerebellar syndrome may occur as a PCS, and scintigraphically as diffuse cerebellar hypermetabolism. At an early disease stage, structural brain imaging is commonly normal.[1] The neoplasms most commonly involved are small cell lung cancer, gynecological (including carcinoma of the fallopian tube) and breast tumors, and Hodgkin lymphomas,[1-5] but it is also described in, for example, carcinoma of the tonsil, gastric adenocarcinoma, and extragonadal germ cell tumors.[6-8] An acute cerebellar syndrome is one of the most common neurological paraneoplastic syndromes and is most likely immune mediated.[1] Indeed, frequently, antineural antibodies in the cerebrospinal fluid and/or serum can be demonstrated. In PCS, an extensive loss of Purkinje cells might be associated with inflammatory infiltrates in the cerebellum.[1] Cerebellar hypermetabolism is not exclusive for PSC. Interestingly, a recent study also showed intense cerebellar hypermetabolism, demonstrated by 18F-FDG PET, in a case with leptomeningeal metastasis associated with an atypical meningioma.[9] The cerebellar metabolism in that particular case is similar to that of our present case; however, cerebellar antibodies such as anti-Yo are not detectable in patients with leptomeningeal metastasis, and clinically PSC can frequently be differentiated leptomeningeal metastases.[9] Also, a recent study showed relatively cerebellar hypermetabolism in patients experiencing amyotrophic lateral sclerosis with frontotemporal dementia. However, in these patients, the cerebellar hypermetabolism is less pronounced than in PCS.[10] This case shows that 18F-FDG PET imaging may be of value in patients in which a PCS is considered, particularly in patients suspicious for an occult malignancy or in which the primary tumor is not detected after routine examinations.