What is the appropriate evaluation and management for a 79-year-old male with acute worsening leg weakness, increased fall risk, and new cognitive and mood changes following lumbar spinal fusion surgery performed two months ago?

Urgent Neuroimaging and Surgical Evaluation Required

This patient requires immediate MRI of the lumbar spine and urgent neurosurgical consultation to rule out epidural hematoma, hardware malposition, or insufficient decompression—the most common causes of acute neurologic deterioration after lumbar fusion.

Critical Time-Sensitive Evaluation

The acute worsening at 2 months post-surgery, while initially improving, represents a red flag for surgical complications. Research shows that lower extremity weakness after posterior lumbar fusion occurs in approximately 0.74% of cases, with specific identifiable causes 1:

• Hardware malposition/loosening (36%)
• Epidural hematoma (30%)
• Insufficient decompression (17%)
• Nerve root edema (17%)

Immediate Diagnostic Workup

1. Obtain urgent MRI lumbar spine with and without contrast to evaluate:

   • Epidural fluid collections or hematoma
   • Hardware position relative to neural elements
   • Adequacy of decompression
   • Nerve root compression or edema

2. CT lumbar spine if MRI contraindicated or to better assess:

   • Screw trajectory and potential breach
   • Hardware loosening
   • Bony alignment

3. Cognitive assessment given the new mood and cognitive changes:

   • Screen for postoperative delirium using validated tools
   • This is critical as delirium increases morbidity, mortality, and length of stay 2

The Cognitive Component Cannot Be Ignored

The combination of motor and cognitive symptoms is particularly concerning. While you're appropriately ruling out medications as a cause, postoperative neurocognitive disorder and delirium are the most common perioperative complications in patients over 65 2. However, in this context with concurrent motor deficits, the cognitive changes may be:

• Secondary to an evolving neurologic complication
• Related to uncontrolled pain (though you note he's not on pain medications—this itself may be problematic)
• A manifestation of systemic infection if hardware infection is present

Management Algorithm

If Imaging Reveals Surgical Complication:

Proceed with urgent surgical exploration. The literature demonstrates that 90% of patients with post-fusion weakness improve with timely secondary surgery when a correctable cause is identified 1. The average time to weakness presentation is 2.9 days post-op, but delayed presentations occur 1, 3.

If No Clear Structural Cause Identified:

This occurs in approximately 55% of cases presenting with new neurologic symptoms 3. In these patients:

1. Optimize pain control with multimodal non-opioid approaches
2. Implement non-pharmacologic delirium prevention strategies 2
3. Avoid antipsychotics unless severe agitation threatens safety 2
4. Consider conservative management with close monitoring—most resolve spontaneously 3
5. Serial neurologic examinations to detect progression

Critical Pitfalls to Avoid

• Do not attribute symptoms to "normal post-operative course" at 2 months out, especially with initial improvement followed by decline
• Do not delay imaging while pursuing conservative management—the window for surgical intervention may be time-sensitive
• Do not overlook infection—surgical site infection occurs in 6% of cases and can present with both neurologic and cognitive symptoms 1
• Do not assume frailty explains everything—while this 79-year-old may be frail (which increases complication risk 4, 5), acute changes demand investigation for reversible causes

Frailty Context

Given his age, assess frailty using the modified Frailty Index. Frail patients have 5.4 times higher odds of postoperative complications 4 and are more prone to delirium (7.5% vs 3.0%) 6. However, even frail elderly patients benefit significantly from lumbar fusion when appropriate 6, so age alone should not deter aggressive evaluation and treatment of complications.

The combination of motor, cognitive, and mood changes in a patient who was initially improving demands urgent action. Most causes are identifiable on imaging 1, and when found, surgical intervention has a 90% success rate 1.