Indian Journal of Nuclear Medicine

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Year
: 2014  |  Volume : 29  |  Issue : 4  |  Page : 282--283

Fludeoxyglucose positron emission tomography-computed tomography in limbic encephalitis


Sushanti Patil, Vikram Lele 
 Department of Nuclear Medicine and PET-CT, Jaslok Hospital and Research Center, Mumbai, Maharashtra, India

Correspondence Address:
Sushanti Patil
405, Mahesh Darshan-2, Link Road, Kandarpada, Dahisar (W), Mumbai - 400 068, Maharashtra
India

Abstract

A 66-year-old male patient presented with low grade fever without chills associated with simple partial seizures. He was advised whole body positron emission tomography-computed tomography (PET/CT) (fluorodeoxyglucose PET/CT) scan which demonstrated an increase in metabolic activity in the limbic system. There was no evidence of active disease anywhere else in the body. Thus, in the setting of limbic encephalitis PET-CT helps in locating the cancerous origin as well as gives information about functional abnormality of the brain.



How to cite this article:
Patil S, Lele V. Fludeoxyglucose positron emission tomography-computed tomography in limbic encephalitis.Indian J Nucl Med 2014;29:282-283


How to cite this URL:
Patil S, Lele V. Fludeoxyglucose positron emission tomography-computed tomography in limbic encephalitis. Indian J Nucl Med [serial online] 2014 [cited 2020 Sep 25 ];29:282-283
Available from: http://www.ijnm.in/text.asp?2014/29/4/282/142651


Full Text

A 66-year-old male patient presented with low grade fever without chills associated with body ache and weakness, irrelevant talk, episodes of anxiety and depression, gradual worsening of memory, and simple partial seizures. The patient's symptoms did not correlate with each other, and his condition seemed to worsen. He was advised whole body positron emission tomography-computed tomography scan. [Figure 1] demonstrates increased metabolism in bilateral caudate nuclei and putamen and in anterior and medial aspect of both temporal lobes. Increase in metabolic activity in the limbic system. [Figure 2] shows that there was no evidence of active disease anywhere else in the body. This picture along with his symptoms helped us conclude that the findings represent ongoing inflammatory pathology most likely limbic encephalitis. The patient's cerebrospinal fluid analysis was performed, which showed an increase in white blood cell and proteins, which confirmed our suspicion.{Figure 1}{Figure 2}

The name limbic encephalitis was coined by Corsellis et al.[1] Limbic encephalitis could be caused either by direct invasion of the brain by an infectious agent, usually a virus (infectious encephalitis) or by the persons own immune system reacting against itself (auto-immune encephalitis). Limbic encephalitis is a rare disorder characterized by personality changes, irritability, depression, seizures, memory loss, and sometimes dementia. The diagnosis is difficult because clinical markers are often lacking. There are two forms of autoimmune limbic encephalitis: Paraneoplastic limbic encephalitis (PLE) and non PLE.

In PLE, most individuals will turn out to have cancer of the lung, thymus gland, lymphatics, the breast, or the testis. The condition may improve or at least stabilize if the cancer is detected and treated effectively; but, unfortunately in many cases, the tumor proves difficult to identify or the treatment does not cure the patient's neurological symptoms. Sixty percent of the time, limbic encephalitis is paraneoplastic in origin. [2] In fact, it is thought that up to 1 in 100 people with cancer have PLE which is commonly misdiagnosed as neurological diseases such as Alzheimer's. [3] The anti-Hu antibody is directed against RNA-associated neuronal proteins and is known to cause paraneoplastic encephalomyelitis/sensory neuronopathy syndrome mostly when associated with small cell lung cancer. [4]

Nonparaneoplastic limbic encephalitis has only been clearly recognized in the recent years. It includes patients who had the symptoms of PLE, but who did not have any of the marker paraneoplastic antibodies in their blood and never developed a tumor. Moreover, some of these patients got better if they were treated with drugs that suppress the immune system. The cause of this is believed to be an antibody that binds to a protein, present in all brain tissue: The potassium channel. This causes a reduction in the number of potassium channels, decreasing the control over electrical signals operating in the brain. Potassium channels are proteins that lie in the surrounding membrane of nerve cells in the brain and in the nerves that lead to the muscles of the skeleton, the gut, and the heart. [5] They are particularly common in the hippocampus and other limbic areas of the brain.

In the setting of limbic encephalitis, fluorodeoxyglucose-PET imaging can be of value from the standpoints: (1) Detection of the occult malignant focus (paraneoplastic neurological syndrome) and (2) objective assessment of the presence and extent of the functional abnormality in the brain and correlation of the imaging findings with the clinical features and disease activity. [6]

References

1Corsellis JA, Goldberg GJ, Norton AR. "Limbic encephalitis" and its association with carcinoma. Brain 1968;91:481-96
2Rowland LP. Merritts Neurology. LWW; Twelfth edition (December 3, 2009). ISBN: 9780781791861.
3Gultekin SH, Rosenfeld MR, Voltz R, Eichen J, Posner JB, Dalmau J. Paraneoplastic limbic encephalitis: Neurological symptoms, immunological findings and tumour association in 50 patients. Brain 2000;123:1481-94.
4Winkler AS, Dean A, Hu M, Gregson N, Chaudhuri KR. Phenotypic and neuropathologic heterogeneity of anti-Hu antibody-related paraneoplastic syndrome presenting with progressive dysautonomia: Report of two cases. Clin Auton Res 2001;11:115-8.
5Vedeler CA, Antoine JC, Giometto B, Graus F, Grisold W, Honnareat J, et al. EFNS guidelines 2011, paraneoplastic neurological syndromes. European Handbook of Neurological Management. 2 nd ed., Vol. 1, Ch. 31. 2011 Blackwell publishing limited, ISBN: 978-1-405-18533-2.
6Basu S, Alavi A. Role of FDG-PET in the clinical management of paraneoplastic neurological syndrome: Detection of the underlying malignancy and the brain PET-MRI correlates. Mol Imaging Biol 2008;10:131-7.