How to manage a 60-year-old male with recurrent transient lower limb weakness, normal computed tomography (CT) brain scan, and no other neurological deficits?

Management of Recurrent Transient Lower Limb Weakness in a 60-Year-Old Male

This patient's recurrent transient lower limb weakness episodes likely represent transient ischemic attacks (TIAs) affecting the lower extremities, requiring urgent vascular evaluation and comprehensive neurological workup to prevent progression to stroke.

Clinical Assessment and Differential Diagnosis

The patient's presentation of recurrent, self-resolving episodes of lower limb weakness without loss of consciousness suggests several possible diagnoses:

Primary Considerations:

• Transient Ischemic Attack (TIA): Most likely diagnosis given the age, recurrent nature, and transient neurological deficit
• Peripheral Arterial Disease (PAD) with exercise-induced claudication: Supported by recent gym activity and knee pain
• Vertebrobasilar insufficiency: Can cause transient lower limb weakness without loss of consciousness

Secondary Considerations:

• Spinal stenosis/radiculopathy: May be exacerbated by exercise
• Metabolic disorders: Though electrolytes are normal
• Seizure disorder: Less likely without loss of consciousness
• Conversion disorder/functional neurological symptoms: Diagnosis of exclusion

Recommended Investigations

Immediate Investigations:

1. Duplex ultrasonography of carotid and vertebral arteries: First-line imaging to detect vascular stenosis 1
2. MRI brain with diffusion-weighted imaging: To identify small infarcts not visible on CT 2
3. MR angiography (MRA) or CT angiography (CTA) from aortic arch to vertex: To evaluate vascular anatomy 1
4. 12-lead ECG and cardiac monitoring: To identify arrhythmias (especially atrial fibrillation) 1
5. Ankle-Brachial Index (ABI): To evaluate for peripheral arterial disease, particularly given the recent exercise and knee pain 1, 3
   • Consider exercise ABI if resting ABI is normal (0.91-1.30) 1

Additional Investigations:

1. Echocardiography: To identify cardiac sources of emboli
2. Lipid profile and HbA1c: To assess cardiovascular risk factors
3. Holter monitoring: To detect paroxysmal arrhythmias
4. Thrombophilia screen: If no other cause is identified, especially in younger patients

Management Approach

Immediate Management:

1. Risk stratification: Calculate ABCD² score to determine stroke risk 2
2. Antithrombotic therapy:
   • For suspected TIA: Start dual antiplatelet therapy (aspirin plus clopidogrel) for first 21 days, then continue with single antiplatelet therapy 1
   • If carotid stenosis is identified: DAPT is recommended for at least 21 days if not revascularized 1

Definitive Management (Based on Investigation Results):

1. If significant carotid stenosis (>70%) is identified:

   • Refer for carotid endarterectomy evaluation if symptoms correspond to the territory of stenosis 1

2. If peripheral arterial disease is diagnosed:

   • Regular follow-up at least annually, assessing clinical and functional status 1
   • Consider revascularization if symptoms are limiting or if critical limb ischemia develops 1

3. If vertebrobasilar insufficiency is diagnosed:

   • Optimize medical management with antiplatelets and risk factor modification

4. If no vascular cause is identified:

   • Consider neurology referral for evaluation of other causes of transient neurological symptoms
   • Consider spinal imaging if radiculopathy is suspected

Prevention Strategies

1. Cardiovascular risk factor modification:

   • Blood pressure control
   • Lipid management
   • Diabetes management if applicable
   • Smoking cessation if applicable
   • Regular physical activity

2. Medication:

   • Antiplatelet therapy (aspirin, clopidogrel, or both initially)
   • Statin therapy
   • Antihypertensives as indicated
   • Consider ACE inhibitors for patients with asymptomatic PAD 1

Follow-up Plan

• Short-term: Reassessment within 1-2 weeks to review investigation results and adjust management
• Long-term: Regular follow-up at least annually if PAD is diagnosed 1
• Monitoring: For recurrent symptoms, progression of weakness, or development of other neurological symptoms

Important Considerations

• TIAs are serious warning signs with a high risk of subsequent stroke, especially in the first 48 hours to 3 months 4, 2
• Rapid evaluation and treatment can significantly reduce the risk of subsequent stroke 1
• Even "asymptomatic" PAD is associated with increased cardiovascular risk and requires aggressive risk factor management 1
• The absence of classic claudication symptoms does not rule out significant vascular disease 1

This patient requires urgent vascular evaluation given the recurrent nature of symptoms and the potential for preventable stroke or limb ischemia.