Hemifacial spasm: Brief, unilateral, sudden jerks involving the face and ipsilateral arm are characteristic of hemifacial spasm, which can sometimes be accompanied by arm involvement due to the spread of the abnormal electrical activity.

Focal dystonia: This condition can cause abnormal movements and postures in the affected limb and face, although the pattern of brief, sudden jerks might be less typical.
Tardive dyskinesia: Although more commonly associated with long-term medication use, tardive dyskinesia can cause abnormal, involuntary movements of the face and limbs.
Partial seizures: Seizure activity limited to one part of the brain can cause focal symptoms such as jerking movements in one limb or side of the face.

Stroke or Transient Ischemic Attack (TIA): Although the presentation might not be typical, any new onset of focal neurological symptoms warrants consideration of a vascular event, given the potential for serious consequences if missed.
Multiple Sclerosis: This condition can cause a wide range of neurological symptoms, including abnormal movements, due to demyelination in the central nervous system.
Brain Tumor: A tumor in the brain could cause focal neurological symptoms, including abnormal movements, by compressing or invading nearby brain tissue.

Wilson's Disease: A genetic disorder that leads to copper accumulation in the brain and liver, causing neurological symptoms including abnormal movements.
Huntington's Disease: An inherited disorder that causes progressive damage to the brain, leading to cognitive, motor, and psychiatric symptoms, including chorea (involuntary, abrupt movements).
Sydenham's Chorea: A rare neurological disorder occurring in some cases of rheumatic fever, characterized by rapid, involuntary movements, primarily of the face and limbs.