What is the cause of intermittent leg spasms and pain in an elderly patient with a history of asthma, which began after a traumatic incident and worsens when sleeping on their side, despite normal vitamin B12 and folate levels and an unspecified HbA1c value?

Diagnosis: Restless Legs Syndrome (RLS) with Nocturnal Leg Cramps

This elderly patient's intermittent leg spasms occurring exclusively during sleep, worsening when lying on their side, with complete relief during walking and daily activities, meets diagnostic criteria for Restless Legs Syndrome (RLS), likely complicated by nocturnal leg cramps. 1

Clinical Reasoning

The presentation satisfies all four essential diagnostic criteria for RLS established by the American Geriatrics Society 1:

1. Urge to move with uncomfortable sensations: Patient reports "uncomfortable spasms" in the right ankle/lower leg 1
2. Symptoms begin/worsen during rest: Spasms occur only when sleeping on side, not during walking or daily activities 1
3. Relief with movement: Complete absence of pain when walking confirms movement provides relief 1
4. Circadian pattern: Symptoms occur exclusively at night during sleep 1

The physical examination showing no tenderness at ankle joints, no calf swelling, and intact neurovascular exam effectively rules out vascular disease, deep vein thrombosis, and peripheral neuropathy as primary causes 1. The mid-tibial tenderness is nonspecific and likely related to muscle spasm rather than structural pathology 2.

Key Differentiating Features

This is NOT simply nocturnal leg cramps because:

• RLS involves dysesthesias and urge to move, while pure cramps do not 2
• The patient describes "spasms" rather than sustained painful muscle contractions typical of cramps 3
• However, the patient also reports "leg cramps when stretching in bed," suggesting both conditions coexist 3

This is NOT peripheral neuropathy because:

• Normal B12 and folate levels make B12-deficiency neuropathy unlikely 4
• Neurovascular exam is intact 1
• No sensory changes or neuropathic pain descriptors are documented 2

Essential Next Steps

1. Check Serum Ferritin Immediately

Obtain serum ferritin level—values <50 ng/mL indicate iron deficiency and warrant iron supplementation. 1, 4 The American Geriatrics Society emphasizes that impaired dopamine transport due to reduced intracellular iron plays a critical role in RLS pathophysiology, and this is the single most important modifiable factor in elderly patients 1, 4.

2. Review HbA1c Value

The documented HbA1c value needs interpretation—if elevated, diabetic neuropathy could be a contributing secondary cause requiring glycemic optimization 2. However, the intact neurovascular exam makes this less likely as the primary etiology 1.

3. Medication Review

Immediately review all current medications for RLS-exacerbating agents. The American Geriatrics Society identifies tricyclic antidepressants, SSRIs, lithium, and dopamine antagonists as common culprits 1, 3. The patient's asthma medications should be continued as respiratory control takes priority 5.

Treatment Algorithm

First-Line: Nonpharmacologic Interventions

Start immediately with lifestyle modifications 1, 3:

• Eliminate caffeine completely, especially after noon 3
• Cease tobacco use if applicable 1, 3
• Avoid alcohol 1, 3
• Implement moderate daily exercise but not within 3 hours of bedtime 1, 3
• Avoid prolonged positioning at end-range joint positions during sleep 2

Second-Line: Iron Supplementation (if ferritin <50 ng/mL)

If serum ferritin is <50 ng/mL, initiate iron supplementation before considering dopaminergic agents 1, 4. This addresses the underlying pathophysiology directly 4.

Third-Line: Dopaminergic Agents (if symptoms persist after 2-4 weeks)

If nonpharmacologic measures and iron supplementation (if indicated) fail, initiate ropinirole or pramipexole. 1, 3

For ropinirole 1:

• Start 0.25 mg orally 1-3 hours before bedtime
• Increase to 0.5 mg after 2-3 days
• Titrate to 1 mg after 7 days
• Maximum 4 mg at week 7 if needed

For pramipexole 1:

• Start 0.125 mg orally 2-3 hours before bedtime
• Titrate as needed

Critical caveat in elderly patients: Monitor closely for orthostatic hypotension, nausea, sleepiness, and compulsive behaviors 1. The American Geriatrics Society emphasizes particular consideration for drug interactions and orthostasis risk in older patients 1.

Special Considerations for This Patient

Asthma Management

Continue current asthma medications without interruption 5. Asthma in elderly patients requires careful monitoring, but there is no contraindication to RLS treatment 5, 6. The patient's asthma appears well-controlled, which is essential before addressing RLS symptoms 5.

Positional Component

The fact that symptoms occur only when sleeping on the side suggests a positional exacerbation 2. Recommend sleeping on back initially while implementing other interventions 2.

Lower Back Pain

The reported lower back pain when transitioning from sitting to standing may represent a separate musculoskeletal issue or could be related to compensatory movements from RLS 1. Address this separately if it persists after RLS treatment 1.

Common Pitfalls to Avoid

1. Do not delay checking ferritin: This is the most commonly missed treatable cause in elderly RLS patients 1, 4
2. Do not start dopaminergic agents without trying nonpharmacologic measures first: Lifestyle modifications alone may be sufficient 1, 3
3. Do not attribute symptoms solely to age or the initial ankle trauma: The trauma may have been coincidental, and the symptom pattern clearly indicates RLS 1
4. Do not overlook medication-induced RLS: Even if the patient is not currently on known culprits, verify all medications including over-the-counter agents 1, 3