Leucine-rich glioma-inactivated 1 (LGI1)-antibody encephalitis can be difficult to diagnose. It should be considered when there is clinical presentation of brief, unilateral jerking of the face and arm, termed faciobrachial dystonic seizures (FBDS), which is a hallmark feature. Additionally, hyponatremia and brain magnetic resonance imaging (MRI) demonstrating insular lesions are helpful, but not always present. In the case described, only FBDS was noted, which was initially diagnosed as focal motor status epilepticus. The diagnosis was achieved with laboratory data.
A 64-year-old male with a history of coronary artery disease, diabetes mellitus type 2, and hypertension presented to the emergency department with left-sided FBDS. Brain MRI revealed right-sided hippocampal sclerosis as well as moderate white matter disease. Electroencephalography (EEG) captured one stereotypical spell with rhythmic activity that spread, concerning for seizures. Keppra was started which decreased the frequency of spells. The patient was then discharged home with follow-up.
One week later, the patient returned following a fall with loss of consciousness. Upon awakening a few minutes after the incident, he reportedly had repetitive uncontrolled movements of the left upper extremity. He was admitted to the intensive care unit for suspected focal motor status epilepticus. Cerebrospinal fluid analysis was inconclusive and Biofire panel was negative. His FBDS with hyponatremia raised suspicion for LGI1-antibody encephalitis. Encephalopathy, Autoimmune/Paraneoplastic Evaluation, Spinal Fluid (ENC2) Mayo Clinic panel was ordered and the patient was started on intravenous (IV) Solumedrol 1 gram daily for 5 days, then IV Immunoglobulin 0.4 grams/kg/day for 5 days, and IV Valproic acid for high suspicion of LGI1-antibody encephalitis. The patient’s labs later returned positive for LGI1-antibody encephalitis. The patient was successfully treated and discharged home with close follow-up.
This case demonstrates the difficulty of diagnosing LGI1-antibody encephalitis. The patient presented with focal seizures and was initially diagnosed with focal tonic-clonic seizures that were seemingly controlled with Keppra. However, the patient returned to the Emergency Department one week later with FBDS symptoms and worsened hyponatremia, which was suggestive of an encephalitis. While in most encephalitis cases there will be atypical findings in CSF, LGI1-antibody encephalitis will typically have normal CSF findings. Serum and CSF markers for autoimmune encephalitis confirmed the diagnosis in our patient. Patients with LGI1-antibody encephalitis exhibit pathognomonic FBDS, which presented in our patient one week after his initial encounter.
With early diagnosis and treatment, patients with LGI1-antibody encephalitis may fare favorably. However, even with treatment, patients may never return to their baseline cognitive function, with serum LGI1 antibodies still detectable in those that recover clinically. This points to the variability of this elusive and poorly understood diagnosis that causes autoimmune encephalitis.
Audience Take Away
- Early recognition of the atypical characteristics of a patient with LGI1-antibody encephalitis for an accurate diagnosis and prompt treatment
- Clinical presentation of faciobrachial dystonic seizures, which may seemingly present initially as focal motor status epilepticus, suggest LGI1-antibody encephalitis
- Value of diagnostic tools such as CMP for hyponatremia, CSF analysis with ENC2 Mayo Clinic panel, EEG, and MRI in the diagnosis of LGI1-antibody encephalitis
- Treatment of LGI1-antibody encephalitis with Keppra, Solumedrol, IVIG, and Valproic acid, which may be variably efficacious