Video 1
Video showing faciobrachial myoclonus with asymmetric involvement of right upper limb more than left upper limb. Notice the tonic neck deviation to left side.
Table 1
Differential diagnoses of faciobrachial myoclonus.
| DIFFERENTIAL DIAGNOSES | POINTS AGAINST THIS DIAGNOSIS |
|---|---|
| Epilepsia partialis continua with secondary generalization [3, 4] | No abnormal movements of lower limbs |
| Faciobrachial dystonic seizures [5, 6, 7] | a) Faciobrachial dystonic seizures is characterized by unilateral short-lived dystonic posturing of face and unilateral upper arm that lifts the affected arm from bed in most cases (movements in our case was clearly bilateral and synchronous with no arm lifting from the bed); b) No behavioral, psychiatric or cognitive impairment which is almost always associated with the cases of faciobrachial dystonic seizures in autoimmune encephalitis; c) Most remarkably, all the abnormal movements and encephalopathy were abolished by correction of hyperglycemia alone without any immunomodulatory therapy, which also refuted the diagnosis of anti-GAD associated myoclonus; d) No imaging abnormality in fronto-ponto-basal ganglia and cerebello-thalamo-cortical networks; and e) Negative auto-antibody profile, including anti-LGI-1 and Caspr-2. |
| Wernicke’s encephalopathy with myoclonus | Serum thiamine level was normal and brain MRI revealed no abnormality |
| Anti-GAD antibody associated limb myoclonus with encephalopathy [17] | Correction of hyperglycemia alone abated myoclonus obviating any need for steroids or immunotherapy |
| Sporadic Creutzfeldt-Jakob disease | Normal MRI brain and cerebrospinal fluid |