What imaging is recommended for a patient with pre-syncope and a history of brain surgeries for Arnold Chiari (Arnell-Chiari malformation) syndrome?

Imaging Recommendations for Pre-syncope in a Patient with Prior Chiari Malformation Surgery

This patient requires MRI of the brain and complete spine with and without IV contrast, including sagittal T2-weighted sequences of the craniocervical junction and phase-contrast CSF flow studies. While ACR guidelines generally recommend against neuroimaging for uncomplicated pre-syncope, this patient's history of two prior brain surgeries for Chiari malformation fundamentally changes the clinical scenario and necessitates comprehensive neuroimaging to evaluate for surgical complications, recurrent tonsillar herniation, hydrocephalus, or syrinx formation.

Primary Imaging Recommendation

MRI brain and complete spine imaging is indicated for this patient based on the following considerations:

• The ACR Appropriateness Criteria state that brain CT and MRI should be avoided in uncomplicated syncope/pre-syncope, as the yield of acute abnormalities is only 5-6.4% in patients without head trauma or focal neurological deficits 1

• However, this is not uncomplicated pre-syncope—the patient has a history of surgically treated Chiari malformation, which represents a "separate neurologic process" requiring a different evaluation course 1

• The Congress of Neurological Surgeons guidelines recommend that in patients with known Chiari malformation, complete brain and spine imaging may be helpful to evaluate for clinically relevant pathology such as hydrocephalus or spine syrinx 1

Specific MRI Protocol Components

The imaging protocol should include:

• Brain MRI with and without IV contrast to assess the surgical site, evaluate for recurrent tonsillar herniation, and identify any complications from prior surgeries 2

• Sagittal T2-weighted sequences of the craniocervical junction to properly assess the relationship between cerebellar tonsils and foramen magnum 2, 3

• Complete spine imaging to evaluate for syringomyelia (syrinx), which occurs in association with Chiari malformation and can cause neurological symptoms including autonomic dysfunction that may manifest as pre-syncope 1, 3

• Phase-contrast CSF flow studies at the craniocervical junction to evaluate for CSF flow obstruction, which is a primary mechanism causing symptoms in Chiari malformation 2, 3

• Gradient echo or susceptibility-weighted sequences to fully evaluate the extent of the malformation and any postoperative changes 2

Rationale for Comprehensive Imaging

Why complete neuraxis imaging is necessary:

• Chiari malformation is characterized by cerebellar tonsillar herniation through the foramen magnum, potentially causing compression or obstruction of CSF flow 1, 3

• MRI provides optimal anatomic detail and may reveal ventriculomegaly (hydrocephalus), characteristics of intracranial hypertension or hypotension, spinal cord syrinx, or tethered spinal cord—all of which can influence management 3, 4

• In patients with prior Chiari surgery, recurrent symptoms may indicate surgical failure, scar tissue formation, or development of new pathology 5

• Syringomyelia occurs commonly with Chiari malformation and can cause autonomic dysfunction that may present as pre-syncope 6, 4

Additional Cardiac Evaluation

Despite the neurological history, cardiac evaluation remains essential:

• This 57-year-old female meets age criteria (>55-60 years) associated with higher risk for cardiac-related syncope 1

• 12-lead ECG should be obtained for all patients with syncope/pre-syncope to detect arrhythmias or abnormalities indicative of higher arrhythmia risk 1

• Cardiac-related syncope carries significantly increased risk of death compared to other etiologies 1

• Transthoracic echocardiography may be appropriate if history, physical examination, or ECG suggest structural heart disease or cardiac etiology 1

Critical Clinical Assessment Points

The evaluation should specifically assess for:

• Postural blood pressure changes to diagnose orthostatic-related syncope 1

• Detailed neurologic examination looking for focal deficits, signs of increased intracranial pressure, or symptoms suggesting recurrent Chiari-related compression (headaches worsened by Valsalva, neck pain, vertigo, nystagmus) 2, 5

• Cardiac examination assessing for structural heart disease, with attention to palpitations or cardiac symptoms prior to the pre-syncopal episode 1

• Signs of head trauma from a fall during the pre-syncopal episode, which would require separate imaging considerations 1

Important Caveats

Common pitfalls to avoid:

• Do not dismiss neuroimaging based solely on general syncope guidelines—the surgical history of Chiari malformation fundamentally alters the risk-benefit calculation 1

• Do not order isolated brain imaging without spine evaluation, as syrinx formation is a critical associated finding that requires complete spine visualization 1, 3

• Do not assume prior surgical correction eliminates the possibility of recurrent or residual Chiari-related pathology 5

• Recognize that symptoms of Chiari malformation can overlap with other conditions and may have periods of exacerbation and remission 5