What causes uncontrolled upper extremity muscle twitching and involuntary arm movements?

Differential Diagnosis of Uncontrolled Upper Extremity Muscle Twitching and Involuntary Arm Movements

The most critical first step is to exclude stroke or seizure as the cause, as these are life-threatening conditions requiring immediate intervention. 1

Immediate Life-Threatening Causes to Rule Out

Acute Stroke/TIA

• Obtain immediate neuroimaging (CT or MRI) if there is sudden onset with associated neurological deficits such as facial droop, dysarthria, sensory loss, weakness, or visual field defects 1
• Involuntary movements from stroke typically involve the contralateral hemisphere, basal ganglia, thalamus, or corpus callosum 1
• Repetitive involuntary movements can result from transient hemodynamic ischemic episodes, particularly with carotid occlusive disease, and are characteristically precipitated by standing, walking, or hyperextension of the neck 2

Focal Motor Seizures

• Focal motor seizures present with synchronous, rhythmic, and numerous (20-100) involuntary movements that may progress to other body parts 1
• Order EEG and obtain neurology consultation if movements are rhythmic, synchronous, and followed by post-ictal confusion or Todd's paralysis 1
• Seizures are very rarely reported in hepatic encephalopathy but must be excluded 3

Primary Movement Disorders

Paroxysmal Kinesigenic Dyskinesia (PKD)

PKD should be strongly considered if the involuntary movements are triggered by sudden voluntary actions and last less than 1 minute. 1

• Episodes are precipitated by sudden voluntary movements, with duration less than 1 minute in over 98% of cases 4, 1
• Approximately 78-82% of patients experience aura described as numbness, tingling, and muscle weakness before attacks 5
• Face involvement occurs in approximately 70% of patients 4
• Attack frequency varies from several times yearly to more than 100 times daily 4
• Age of onset typically ranges from several months to 20 years, with high incidence among 7-15 year-olds 5
• PRRT2 gene mutations account for the majority of cases and genetic testing should be ordered 5

Tardive Dyskinesia

• Associated with long-term use of dopamine receptor-blocking agents (primarily antipsychotics) 4
• Characterized by choreoathetoid movements typically affecting the orofacial region (70% of patients), limbs, and trunk 4
• Causes facial twitching, rigidity of facial muscles, and dysarthria 4
• If clinically feasible, gradually withdraw the offending antipsychotic medication 4
• Consider switching to atypical antipsychotics with lower D2 affinity when antipsychotic treatment must continue 4

Hepatic Encephalopathy

• Asterixis ("flapping tremor") is a negative myoclonus consisting of loss of postural tone, easily elicited by hyperextension of the wrists with separated fingers 3
• Can be observed in the feet, legs, arms, tongue, and eyelids 3
• Extrapyramidal dysfunction includes hypomimia, muscular rigidity, bradykinesia, hypokinesia, and parkinsonian-like tremor 3
• Involuntary movements similar to tics or chorea occur rarely 3
• Asterixis is not pathognomonic of hepatic encephalopathy and can be observed in other diseases such as uremia 3

Restless Legs Syndrome (RLS)

• Characterized by an urge to move one or both legs (and sometimes the arms) when immobile, often associated with dysesthesias 3
• Relieved by movement and most prominent in the evening or at night 3
• Clinically significant RLS occurs at least once a week and is present in 2-3% of adults 3

Metabolic and Toxic Causes

Vitamin B12 Deficiency

• Myoclonus-like muscular contractions can appear soon after initiation of B12 therapy and disappear after the first week 6
• Involuntary movements should be considered as one of the extraordinary neurological manifestations of B12 deficiency in adults 6

Diagnostic Algorithm

Step 1: Assess for stroke/TIA

• Sudden onset with associated neurological deficits → immediate CT/MRI 1

Step 2: Assess for seizure

• Rhythmic, synchronous, numerous movements with post-ictal state → EEG and neurology consultation 1

Step 3: Characterize the movement pattern

• Brief episodes (<1 minute) triggered by sudden movements → consider PKD 4, 1
• Flapping tremor with hyperextension of wrists → consider hepatic encephalopathy or uremia 3
• Orofacial movements with antipsychotic history → consider tardive dyskinesia 4
• Urge to move with evening predominance → consider RLS 3

Step 4: Order targeted investigations

• MRI brain for suspected stroke 1
• EEG for suspected seizures 1
• PRRT2 genetic testing for suspected PKD 5
• Liver function tests and ammonia level for suspected hepatic encephalopathy 3
• Vitamin B12 level for suspected deficiency 6
• Medication review for tardive dyskinesia 4

Common Pitfalls

• Do not assume all involuntary movements are benign movement disorders without first excluding stroke and seizures 1
• Asterixis is often mistakenly considered pathognomonic for hepatic encephalopathy, but it occurs in uremia and other metabolic conditions 3
• Bilateral symptoms are atypical for most focal neurological conditions and warrant expanded differential diagnosis 5
• Mental and motor signs of hepatic encephalopathy may not progress in parallel in each individual, producing difficulties in staging severity 3