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Table 1: Clinical symptoms and images information before and after treatment
Stage Presenting symptoms CSF MRI Tumor screening
First GTCS, aggressive behavior, memory WBC 12/μL Bilateral increased T2 signal in Enlarged mediastinal
admission impairment, confusion Protein 60.1 mg/dL the medial temporal lobe lymph nodes
Glc 4.30 mmol/L
After Mild memory impairment ‑ Mild increased T2 signal ‑
treatment (1‑month outpatient follow‑up)
Second Aggressive behavior, distinct memory WBC 4/μL Mild increased T2 signal SCLC
admission impairment (milder than the first admission) Protein 40.2 mg/dL (severer than the follow‑up image)
Glc 3.63 mmol/L
CSF: cerebrospinal fluid, MRI: magnetic resonance imaging, GTCS: generalized tonic‑clonic seizure, WBC: white blood cell, Glc: glucose, SCLC: small cell lung cancer

for central nervous system (CNS) autoantibodies testing
revealed CSF antibodies to GABA-B receptor (IgG 1:100).
Other tested CNS autoantibodies, including
anti-leucine-rich glioma inactivated-1 (LGI1) receptor,
anti-contactin-associated protein-like 2 receptor,
anti-N-methyl-D-aspartate receptor, anti-a-amino-3-h
a b ydroxy-5-methyl-4-isoxazolepropionic acid receptor,
rheumatological autoantibodies, thyroid function tests,
anti-thyroglobulin and thyroid peroxidase antibodies
were all negative. Tumor marker tests revealed elevated
CA125 of 35.2 U/mL and mild elevated of NSE of
25.7 ng/mL. A repeated chest CT showed a mass in
right hilus pulmonis, which was finally confirmed
c to be SCLC by biopsy. Unfortunately, the patient and
Figure 1: Brain magnetic resonance imaging screens in anti‑gamma‑ his carers refused further immunomodulating or
aminobutyric‑acid B receptor encephalitis: (a) revealed bilateral increased T2 antineoplastic treatments. He was discharged with
signal in the medial temporal lobe at the first admission; (b) showed milder
increased T2 signal 1 months after the first discharge; (c) revealed the lesion memory impairment, which was persisted after another
worsen again at the second admission
3 months follow-up.
admission. A repeated brain MRI was performed DISCUSSION
on day 20 and revealed even severer bilateral
fluid-attenuated inversion recovery (FLAIR) and The misdiagnosis rate of anti-GABA-B receptor
T2 hyperintensity in the medial temporal lobe. encephalitis is high since autoantibodies tests were
Therefore, intravenous immunoglobulins (IVIg) still not popularized in many countries. Most recently,
(400 mg/kg/day) was administered for 5 days on day case serials of patients with anti-GABA-B receptor
20. The patient developed significant improvement encephalitis emphasized the typical triad of clinical
of limbic dysfunction during the IVIg therapy. presentation, including memory alternation, seizures,
Although no occupying lesion was found in lung, we and SCLC. There are numbers of SCLC-associated
[6]
suggested further tumor screening including biopsy onconeural antibodies, including Hu, amphiphysin,
of mediastinal lymph nodes and fluorodeoxyglucose and collapsin response-mediator protein (CV2).
positron emission tomography. However, the patient Anti-GABA-B receptor antibodies may be detected
refused further extensive screen for underlying tumor in patients with LE associated with SCLC who are
and was discharged 25 days after admission, with full seronegative for other onconeural antibodies. The
[7]
recovery of behavior and mental status, and partially mechanism of SCLC-associated autoimmune responses
improvement of memory impairment. One month after remains to be elucidated. It may be related to abnormal
discharge, the follow-up brain MRI showed the lesion self-antigen expression in tumor cells, or the antigenic
in remission [Figure 1]. protein might be mutated or modified to those foreign
to the immune system. Neurological symptoms often
The patients remained no recurrence of seizure and present before the cancer becomes symptomatic,
stable LE symptom during nearly 3 months follow-up. suggesting the importance of early detection and
However, he was found collapsed 4 months after diagnosis of SCLC. The paraneoplastic cases with
discharge, with subsequent recurrence of the abnormal anti-GABA-B encephalitis, particularly SCLC, presented
behavior, disorientation, and worsening of memory at an older age range from 53 to 75 years old, and had
impairment. Brain MRI revealed distinct lesions male predominance. [1,4] Paraneoplastic cases seemed
again [Figure 1]. CSF analysis revealed normal levels to have higher titers antibodies, mostly higher than
of protein, white blood, and glucose [Table 1]. Results 1:100 (IgG) in CSF. [1,4,8]

188 Neuroimmunol Neuroinflammation | Volume 2 | Issue 3 | July 15, 2015 Neuroimmunol Neuroinflammation | Volume 2 | Issue 3 | July 15, 2015 189