From the Guidelines
For occipital headaches, the recommended initial imaging study is typically a magnetic resonance imaging (MRI) of the brain with and without contrast, as it provides detailed visualization of brain tissue, blood vessels, and potential abnormalities in the occipital region 1. When considering the best imaging modality for occipital headaches, several factors come into play, including the severity and nature of the headache, as well as the presence of any neurological symptoms.
Key Considerations
- Severity and Nature of Headache: If the headache is sudden and severe (thunderclap headache), a computed tomography (CT) scan may be ordered first due to its speed and availability, especially to rule out acute hemorrhage 1.
- Neurological Symptoms: The presence of neurological symptoms such as confusion, seizures, or focal neurological deficits would necessitate immediate imaging, potentially with a CT scan if MRI is not readily available.
- Preferred Imaging Modality: MRI is generally preferred for occipital headaches as it better visualizes the posterior fossa, cerebellum, and brainstem structures that may be involved in occipital pain.
Conditions Detected by MRI
MRI can detect various conditions that cause occipital headaches, including:
- Arnold-Chiari malformations
- Occipital neuralgia
- Posterior circulation aneurysms
- Arteriovenous malformations
- Tumors
- Multiple sclerosis plaques If vascular pathology is specifically suspected, MR angiography (MRA) or MR venography (MRV) may be added to evaluate blood vessels 1.
When Imaging May Not Be Necessary
Imaging may not be necessary for typical tension-type or migraine headaches with normal neurological examinations, but should be considered when headaches are persistent, severe, associated with neurological symptoms, or unresponsive to appropriate treatment. Given the most recent and highest quality evidence, MRI of the brain with and without contrast is the recommended initial imaging study for occipital headaches, unless the clinical presentation suggests a need for immediate evaluation of acute hemorrhage, in which case a CT scan may be more appropriate 1.
From the Research
Imaging Studies for Occipital Headache
- The initial imaging study for an occipital headache is a noncontrast computed tomography (CT) brain scan 2
- If the CT scan is negative, a lumbar puncture (LP) and cerebrospinal fluid (CSF) analysis may be recommended to rule out subarachnoid hemorrhage (SAH) 2, 3
- Magnetic resonance imaging (MRI) with magnetic resonance angiography (MRA) or computed tomography with computed tomography angiography (CTA) may also be considered as alternative diagnostic strategies for SAH 4
- The choice of imaging study may depend on patient factors, presentation factors, and institutional factors, such as the availability of MRI with MRA 4
Diagnostic Utility of Imaging Studies
- Noncontrast CT brain scan has a high negative predictive value for SAH, reducing the post-test probability of having an angiogram-positive SAH to 0.21% 2
- LP has a high enough proportion of positive results to warrant its continued use after a negative CT head for a patient presenting with a sudden-onset severe headache 3
- MRI pulse sequences, such as fluid-attenuated inversion recovery (FLAIR) and gradient-echo (GE) T2*-weighted images, may be useful in detecting SAH, particularly in the subacute or chronic stages 5