In a 70-year-old woman with a brief, self-limited loss of sensation in both feet and a creatine kinase level of 241 U/L, what is the appropriate initial evaluation and management?

Initial Evaluation and Management

In a 70-year-old woman with transient bilateral foot numbness that resolved spontaneously and a CK of 241 U/L (mildly elevated), the priority is to evaluate for diabetic peripheral neuropathy, peripheral arterial disease, and other causes of transient sensory loss, while recognizing that this CK level does not require immediate intervention or statin discontinuation if she is on lipid-lowering therapy.

Understanding the CK Level

The CK of 241 U/L is only mildly elevated. According to established guidelines:

• CK <4x upper limit of normal (ULN) without symptoms does not warrant stopping statin therapy if the patient is on one 1
• The European Federation of Neurological Societies defines clinically significant hyperCKemia as ≥1.5x ULN, with values ≥3x ULN warranting more aggressive investigation 2
• This level (241 U/L) is likely <3x ULN and does not suggest rhabdomyolysis, myositis, or significant muscle injury 1, 3

Key consideration: CK can be transiently elevated from recent physical activity, and up to 20% of normal individuals have mildly elevated CK 2. This level does not explain her neurological symptoms.

Evaluating the Transient Sensory Loss

The brief, self-limited bilateral foot numbness requires systematic evaluation for:

1. Diabetic Peripheral Neuropathy (Most Likely)

Perform immediate screening 4, 5:

• 10-g monofilament testing on both feet (most important screening tool)
• Vibration sensation using 128-Hz tuning fork (large-fiber function)
• Pinprick or temperature sensation (small-fiber function)
• Check for loss of protective sensation - inability to detect the 5.07 (10g) monofilament indicates significant neuropathy 6

Obtain fasting glucose and HbA1c if not recently checked, as up to 50% of diabetic peripheral neuropathy may be initially asymptomatic 5.

2. Peripheral Arterial Disease

Assess for vascular compromise 7, 4:

• Palpate dorsalis pedis and posterior tibial pulses bilaterally
• Check capillary refill time, rubor on dependency, pallor on elevation
• Ask specifically about claudication (leg fatigue, cramping with walking that resolves with rest within 10 minutes)
• If pulses are diminished or history suggests PAD, obtain ankle-brachial index (ABI) with toe pressures 8, 4

3. Other Neurological Causes

• Deep tendon reflexes in lower extremities (reduced in peripheral neuropathy) 6
• Position sense testing
• Screen for autonomic neuropathy: ask about orthostatic dizziness, check for orthostatic hypotension (≥20 mmHg drop in systolic BP on standing) 5

Management Algorithm

If Neuropathy is Confirmed:

• Optimize glycemic control if diabetic (most effective intervention) 7
• Educate on daily foot inspection using mirror or palpation 4
• Recommend well-fitted walking shoes or therapeutic footwear 7
• Annual comprehensive foot examinations going forward, or more frequently if high-risk features present 4

If PAD is Suspected:

• Refer for vascular assessment if ABI is abnormal or claudication is present 7
• Consider supervised exercise program and smoking cessation if applicable 8

Regarding the Elevated CK:

Do not pursue aggressive muscle disease workup at this CK level unless 1:

• CK rises to ≥4x ULN on repeat testing
• Patient develops muscle pain, weakness, or dark urine
• CK continues to rise on serial monitoring

If patient is on a statin 1, 3:

• Continue the statin - this CK level does not warrant discontinuation
• Recheck CK in 4-6 weeks only if symptoms develop
• Consider transient elevation from exertion or other causes

Critical Pitfalls to Avoid

1. Do not attribute the sensory symptoms to the mildly elevated CK - they are unrelated
2. Do not stop statins based on this CK level alone without muscle symptoms 1
3. Do not miss diabetic neuropathy - it affects up to 50% of diabetics and is often asymptomatic initially 5
4. Do not overlook PAD - many patients are asymptomatic despite significant disease 7, 4
5. Do not delay foot care education - loss of protective sensation dramatically increases ulceration and amputation risk 4

Follow-Up Testing

• Repeat CK only if muscle symptoms develop or if initially pursuing myopathy workup
• Annual monofilament testing and comprehensive foot examination 4
• Fasting glucose/HbA1c if diabetes status unknown
• ABI if vascular symptoms or absent pulses 4