What is the recommended workup for a 63-year-old female on post-operative day 1, status post Anterior Cervical Discectomy and Fusion (ACDF) C4-C7, presenting with a unilateral fixed constricted pupil and mild headache?

Urgent Neuroimaging is Essential for Unilateral Fixed Constricted Pupil After ACDF

For a 63-year-old female with unilateral fixed constricted pupil on post-operative day 1 after ACDF C4-C7, urgent CT or MRI of the brain and cervical spine is required to rule out intracranial bleeding.

Immediate Evaluation

• A unilateral fixed pupil in the post-operative period after ACDF requires urgent neuroimaging as it may represent a neurological emergency 1
• The presence of a mild headache with pupillary changes raises concern for possible intracranial pathology that requires immediate attention 1
• CT brain without contrast should be the first imaging study to quickly rule out intracranial hemorrhage 2
• This should be followed by MRI brain and cervical spine to evaluate for more subtle pathologies if CT is negative 2

Differential Diagnosis

Intracranial Bleeding

• Unilateral pupillary abnormalities can be an early sign of uncal herniation from intracranial bleeding 1
• Although typically presenting with pupillary dilation, intracranial bleeding can occasionally present with pupillary constriction depending on the location 1
• The combination of headache and pupillary changes after surgery is concerning for possible intracranial pathology 3

Surgical Complications

• Direct injury to sympathetic chain during ACDF can cause Horner syndrome (miosis, ptosis, anhidrosis) with an incidence of approximately 0.45-0.6% 4
• C4-C7 levels (as in this patient) are common locations for Horner syndrome development after ACDF 4
• If Horner syndrome is suspected, look for associated ptosis and anhidrosis on the same side as the miotic pupil 4

Other Considerations

• Pituitary apoplexy can present with unilateral pupillary changes and headache in the post-operative period 5
• Migraine or other primary headache disorders can cause transient pupillary changes but would be a diagnosis of exclusion 6
• Medication effects (particularly opioids used for post-operative pain control) can cause pupillary constriction, but this would typically be bilateral 1

Management Algorithm

1. Immediate assessment:

   • Check vital signs including blood pressure and neurological status 1
   • Evaluate for other signs of increased intracranial pressure (altered mental status, nausea/vomiting) 1
   • Document pupil size, shape, and reactivity in both eyes 1
   • Assess for associated ptosis or anhidrosis (suggesting Horner syndrome) 4

2. Urgent neuroimaging:

   • Order stat non-contrast CT head to rule out hemorrhage 2
   • If CT is negative, proceed with MRI brain and cervical spine 2
   • Include dedicated imaging of the surgical site to evaluate for hematoma or other complications 2

3. Neurosurgical consultation:

   • Obtain urgent neurosurgical evaluation regardless of imaging findings 1
   • The combination of new pupillary changes and headache after cervical surgery requires expert assessment 1

4. Management based on findings:

   • If intracranial bleeding: elevate head of bed to 30°, consider osmotic therapy, maintain adequate oxygenation 1
   • If surgical site hematoma: possible return to operating room for evacuation 2
   • If Horner syndrome without other complications: conservative management with expectant observation 4

Prognosis

• If Horner syndrome is diagnosed, approximately 82% of patients experience at least partial resolution within one year (60.7% complete resolution) 4
• Prognosis for intracranial bleeding depends on early diagnosis and intervention 1
• Pupillary changes may be transient if related to surgical manipulation without permanent damage 4

Important Considerations

• Do not attribute pupillary changes to simple post-operative headache without thorough investigation 1
• Serial neurological examinations are essential to monitor for progression of symptoms 1
• The absence of other neurological deficits does not rule out serious pathology, as pupillary changes can be an early isolated finding 1
• Maintain a high index of suspicion for intracranial pathology even if the initial imaging is negative 3