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Images in Neurology
May 11, 2020

Paraneoplastic Encephalomyelitis With Glutamic Acid Decarboxylase Antibodies Presenting as Longitudinal Pyramidal Tract Hyperintensity

Author Affiliations
  • 1Geriatrics and Palliative Care Department, Hospital General de L’Hospitalet de Llobregat–Consorci Sanitari Integral, L’Hospitalet de Llobregat, Barcelona, Spain
  • 2Movement Disorders Unit, Neurology Department, Hospital Sant Joan Despí Moisès Broggi–Consorci Sanitari Integral, Sant Joan Despì, Barcelona, Spain
  • 3Parkinson Unit, Centro Médico Teknon–Grupo Quiron Salud, Barcelona, Spain
  • 4Neuro-Oncology Unit, Neurology Department, Hospital Universitari de Bellvitge–Institut Català d´Oncologia–IDIBELL, L’Hospitalet de Llobregat, Barcelona, Spain
JAMA Neurol. Published online May 11, 2020. doi:10.1001/jamaneurol.2020.0940

A 62-year-old man presented with a 3-month history of progressive weakness in his limbs, anorexia, and weight loss. He reported smoking cigarettes and experiencing chronic lumbar pain and right leg paresis because of a past stroke. Neurological examination showed right facial droop involving the forehead, absent gag reflex, right VI cranial nerve paresis, paraparesis with hyperreflexia, and bilateral Babinski sign without sensory alteration or a sensory level. A cranial and spinal cord magnetic resonance imaging (MRI) with gadolinium revealed T2-weighted and fluid-attenuated inversion recovery (FLAIR) hyperintensities in the right frontoparietal white matter and centrum semiovale (Figure 1A). Abnormal hyperintensity was also present in the middle third of the corpus callosum, and it extended along the right pyramidal tract to the spinal cord, mainly at cervical and upper dorsal level (Figure 1B and Figure 2). Mild contrast enhancements were present in cranial and spinal cord lesions. A right pulmonary hilum tumor, paratracheal and precarinal mediastinal adenopathy, and several costal and pleural metastases were also identified by MRI. The biopsy results were compatible with small cell lung cancer. Examination of the cerebrospinal fluid (CSF) revealed elevated protein content of 0.13 g/dL (to convert to grams per liter, multiply by 10.0), mild pleocytosis (15 leukocytes/mm3, of which most were lymphocytes), and a normal glucose level. Glutamic acid decarboxylase 65 (GAD65) antibodies were detected in serum (1342 U/mL) and CSF (28 870 U/mL). The remaining onconeuronal antibodies (anti-Hu, anti-Yo, anti-Ri, anti-CV2, antibodies against paraneoplastic antigen Ma2 [anti-Ma2, also known as anti-Ta], amphiphysin, recoverin, Sry-like high mobility group box [anti-SOX1], titin, anti-Zic4, anti-Tr [target of Delta/notch-like epidermal growth factor-related receptor (DNER)]) were not present. An extensive CSF workup, including cytological testing and testing for oligoclonal IgG bands and anti–neuromyelitis optica antibodies, had negative results. The patient was diagnosed with definite paraneoplastic neurological syndrome based on the presence of paraneoplastic encephalomyelitis (PEM) and small cell lung cancer along with serum and CSF GAD65 antibodies. He received a 1-g bolus of methylprednisolone daily for 5 days, with partial neurological improvement. Because of the advanced stage of his neoplasia, 2 cycles of carboplatin-etoposide were performed as palliative chemotherapy. He died 4 months after diagnosis.

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    1 Comment for this article
    GAD in the Pyramidal System
    Ayman Alboudi, MD | Mercy Health Saint Mary, MSU
    The article is very interesting, with great images. However, a question would come to my mind: GAD is found in GABAergic neurons, and as far as we know pyramidal cells are not GABAergic.

    Do you have an explanation for the specific high signal on MRI brain affecting the pyramidal system? Is it possible it is a different auto-antibody? I know you checked a lot of antibodies; however, everyday there is a new auto-antibody and there are some more we don't know about.
    CONFLICT OF INTEREST: None Reported
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