What is the differential diagnosis for a 62‑year‑old woman with tremor, clonus, impaired tandem gait, falls, and shoulder collisions, who has moderate‑to‑severe cervical foraminal stenosis at C4‑C6 with radiculopathy, a congenitally narrow spinal canal due to short pedicles (minimum anteroposterior dimension 8 mm), and a recent normal head and neck computed tomography angiography?

Differential Diagnosis: Cervical Myelopathy with Congenital Stenosis

This patient has cervical spondylotic myelopathy (CSM) secondary to severe foraminal stenosis superimposed on congenital canal narrowing, and the tremor, clonus, gait instability, and falls are upper motor neuron signs indicating spinal cord compression rather than isolated radiculopathy. 1

Primary Diagnosis: Cervical Spondylotic Myelopathy

The constellation of findings—hand tremor, clonus, failed tandem gait, falls, and shoulder collisions—represents classic myelopathic features in the context of severe cervical stenosis. 2

Key Diagnostic Features Supporting Myelopathy:

• Congenital canal narrowing (8 mm AP diameter) dramatically increases myelopathy risk, as diameters <13 mm predispose to pathological cord compression with even mild degenerative changes 1, 3
• Clonus is a pathognomonic upper motor neuron sign indicating spinal cord dysfunction 1
• Gait instability and falls in cervical stenosis strongly suggest myelopathic involvement rather than radiculopathy alone 1, 2
• Contralateral symptoms (shoulder collisions, bilateral coordination problems) indicate central canal compromise affecting bilateral corticospinal tracts 1
• Hand tremor in the setting of congenital cervical stenosis may represent an early myelopathic sign rather than essential tremor 1

The combination of moderate-to-severe foraminal stenosis at C4-C6 with short pedicles creates a "double-crush" phenomenon where both radicular and myelopathic compression coexist. 4, 5

Critical Differential Considerations

1. Cervical Radiculopathy Alone (Less Likely)

While the patient has documented radiculopathy, isolated nerve root compression does not explain:

• Clonus (requires corticospinal tract involvement) 1
• Bilateral gait dysfunction 2
• Contralateral motor coordination problems 1

Radiculopathy typically presents with dermatomal pain, weakness in specific myotomes, and reflex changes—not generalized gait instability or clonus. 4, 6

2. Essential Tremor (Unlikely Primary Diagnosis)

Essential tremor is postural/kinetic, bilateral, and symmetric, typically affecting hands during action. 7, 8 However:

• This patient's tremor occurs with clonus and myelopathic signs, suggesting spinal cord origin 1
• Essential tremor does not cause gait instability of this severity or falls 7
• The presence of upper motor neuron signs excludes isolated essential tremor 1

3. Parkinson's Disease (Consider but Less Likely)

Parkinsonian tremor is typically:

• Resting tremor (4-6 Hz) 7, 8
• Associated with bradykinesia, rigidity, and postural instability 7

Key distinguishing features:

• Clonus is not a feature of Parkinson's disease 1
• Normal head/neck CTA makes vascular parkinsonism unlikely 5
• The temporal relationship between cervical stenosis and neurological decline favors myelopathy 2

4. Multiple Sclerosis or Demyelinating Disease (Possible but Less Likely)

While MS can cause:

• Tremor, spasticity, and gait dysfunction 5
• Myelopathic findings 5

Against MS in this case:

• Age 62 with acute/subacute presentation is atypical for new-onset MS 5
• Structural cervical pathology fully explains symptoms 1, 2
• Normal CTA argues against inflammatory CNS vasculopathy 5

5. Spinal Cord Ischemia (Consider)

Anterior spinal artery syndrome can cause acute myelopathy, but:

• Normal CTA makes large vessel disease unlikely 5
• Gradual progression (falls, bumping into walls) suggests chronic compression rather than acute vascular event 5
• Ischemic myelopathy typically presents with sudden-onset paraparesis, not insidious progression 5

6. Epidural Abscess or Hematoma (Exclude Urgently)

These cause acute extrinsic cord compression and require emergency imaging. 5 However:

• No mention of fever, recent procedures, or anticoagulation
• Subacute/chronic presentation less consistent with abscess 5
• MRI cervical spine with contrast is mandatory to exclude 5

Diagnostic Algorithm

Immediate Steps:

1. Obtain MRI cervical spine with and without contrast to:

   • Confirm cord compression and signal changes 5, 2
   • Exclude epidural abscess, hematoma, or tumor 5
   • Assess for T2 hyperintensity indicating myelomalacia 2

2. Perform EMG/nerve conduction studies to:

   • Document radiculopathy severity 1
   • Identify subclinical contralateral radiculopathy 1
   • Abnormal EMG in cervical stenosis predicts progression to symptomatic myelopathy 9, 1

3. Assess for additional upper motor neuron signs:

   • Hoffmann's sign, Babinski sign, hyperreflexia 1, 2
   • Bowel/bladder dysfunction (indicates severe myelopathy) 1, 2

Risk Stratification:

This patient has high-risk features for irreversible myelopathy:

• Congenital stenosis (8 mm diameter) with superimposed degenerative disease 1, 3
• Progressive symptoms with falls and functional decline 9, 2
• Upper motor neuron signs (clonus) indicating established cord dysfunction 1

Prolonged severe stenosis leads to demyelination and necrosis of spinal cord white and gray matter, resulting in potentially irreversible deficits. 9

Management Recommendation

Surgical decompression is strongly recommended for this patient with moderate-to-severe symptoms and established myelopathy, as nonoperative measures have low success rates in established CSM. 9, 1

Surgical Considerations:

• Multilevel foraminal stenosis (C4-C6) with congenital canal narrowing requires addressing both central and foraminal compression 1
• Posterior laminoforaminotomy is effective for foraminal stenosis with radiculopathy 4
• However, central canal stenosis with myelopathy may require laminoplasty or combined anterior-posterior approach depending on alignment and compression pattern 10
• In patients with abnormal EMG and clinical radiculopathy in the setting of stenosis, early decompression prevents progression to symptomatic myelopathy 9, 1

Common Pitfalls:

• Do not delay surgery in established myelopathy—long-standing compression causes irreversible cord damage 9
• Do not attribute all symptoms to radiculopathy alone when upper motor neuron signs are present 1
• Do not miss coexisting myelopathy in patients presenting with radicular complaints—examine for clonus, gait dysfunction, and Hoffmann's sign 1, 2
• Congenital stenosis (<13 mm) accelerates degenerative myelopathy—these patients require lower threshold for surgical intervention 1, 3, 11