What is the appropriate management for a patient presenting with tingling in the left scapula, weakness in the left hand, and suspected upper motor neuron (UMN) signs?

Management of Suspected Upper Motor Neuron Signs with Unilateral Weakness

Obtain urgent MRI of the cervical spine and brain without IV contrast to exclude structural lesions (cervical myelopathy, cord compression, stroke), followed by electrodiagnostic studies to confirm motor neuron involvement and distinguish between pure UMN disease versus combined UMN/LMN pathology. 1, 2, 3

Initial Diagnostic Workup

Immediate Imaging

• MRI brain without IV contrast is the optimal initial imaging modality to exclude stroke, mass lesions, or other structural causes of UMN signs 1, 2, 3
• MRI cervical spine without IV contrast is equally critical given the unilateral scapular and hand symptoms, to exclude cervical myelopathy, syringomyelia, or cord compression 3
• Look for abnormal T2/FLAIR signal in the corticospinal tracts (particularly posterior limb of internal capsule and cerebral peduncles) suggesting UMN degeneration 1, 2, 3
• Assess for "snake eyes" appearance on T2/STIR images of the spinal cord anterior horns, though this finding appears late and is not specific 2, 3

Critical Clinical Assessment

Do not rely on clinical examination alone to establish the diagnosis—the presence of tingling (a sensory symptom) should prompt reconsideration of pure motor neuron disease, as sensory pathways are not involved in typical UMN or LMN lesions 2

Specifically examine for:

• Spasticity (increased muscle tone with velocity-dependent resistance) 1, 2
• Hyperreflexia (brisk or exaggerated deep tendon reflexes) 1, 2
• Clonus (rhythmic muscle contractions with sudden stretch) 1, 2
• Extensor plantar response (Babinski sign) 1, 2
• Any signs of lower motor neuron involvement: fasciculations, muscle atrophy, hyporeflexia, or flaccid weakness 1, 2

Mandatory Electrodiagnostic Studies

EMG and nerve conduction studies are absolutely mandatory to confirm lower motor neuron involvement, as clinical examination alone is insufficient 2, 4

• EMG findings suggesting LMN disease include fibrillation potentials, positive sharp waves, fasciculations, and complex repetitive discharges 1, 2
• Nerve conduction studies showing normal or low compound muscle action potential amplitudes with relatively normal conduction velocities suggest LMN involvement 1, 2
• Abnormal central motor conduction on transcranial magnetic stimulation can detect UMN degeneration in 71% of patients without definite clinical UMN signs, making it valuable when the diagnosis is uncertain 5

Laboratory Evaluation

• Measure creatine phosphokinase (CK) when LMN involvement with weakness is identified 1, 2
• Check thyroid function tests and electrolytes to exclude metabolic causes 1

Risk Stratification for Prognosis

Features Suggesting Primary Lateral Sclerosis (Pure UMN, Better Prognosis)

• Strength ≥4+ in all muscles at initial evaluation strongly suggests PLS rather than ALS 6
• Limb onset (rather than bulbar onset) 6
• Slower progression with longer time to evaluation 6

Features Predicting Development of LMN Signs (ALS, Worse Prognosis)

• Any muscle with strength ≤4 is highly associated with eventual ALS diagnosis 6
• Focal muscle weakness or bulbar onset at baseline 6
• Weight loss (even when controlled for dysphagia and muscle atrophy) 6
• Reduced forced vital capacity 6
• Hyporeflexia in any region 6

Ongoing Management Strategy

Initiate multidisciplinary care immediately involving neurology, pulmonology, nutrition, physical therapy, occupational therapy, speech-language pathology, social work, and palliative care, as this approach improves both survival and quality of life 1, 2, 3

Monitoring Protocol

Perform periodic evaluations (every 3-6 months) assessing:

• Muscle strength in all limbs 6
• Weight 6
• Forced vital capacity 6
• ALS Functional Rating Scale score 6
• Repeat EMG, as changes in any parameter can signal imminent development of LMN signs 6

Respiratory Management

• Implement non-invasive ventilation (NIV) when respiratory insufficiency develops, as this improves median survival and quality of life 1, 2, 3
• Maintain high suspicion for pneumonia and respiratory infections, as patients with motor neuron disease are at very high risk 1, 2

Critical Pitfalls to Avoid

• The presence of sensory symptoms (tingling in scapula) is atypical for pure motor neuron disease and should prompt consideration of alternative diagnoses such as cervical radiculopathy, myelopathy, or combined system degeneration 2
• Do not delay imaging—structural lesions (cervical disc herniation, cord compression, syrinx) can mimic motor neuron disease and require urgent intervention 3
• Unilateral presentation is unusual for classic ALS but can occur; asymmetric weakness at onset does not exclude the diagnosis 6
• Weakness ≤4 in any muscle group strongly predicts progression to ALS rather than benign PLS, requiring more aggressive monitoring and earlier multidisciplinary intervention 6