Is a Computed Tomography (CT) scan of the brain bad?

From the Guidelines

A CT scan of the brain is not recommended for initial assessment of patients with presumptive sudden sensorineural hearing loss (SSNHL) due to its potential significant adverse events and lack of useful information for initial management. The use of CT scans in this context has been deemed "usually not appropriate" by the American College of Radiology (ACR), with a rating of 3, indicating a high risk-benefit ratio for patients 1. This is because CT scans expose patients to radiation, with a relative radiation level (RRL) of 3, and may not provide any useful information for initial management of SSNHL.

Instead, MRI scans are preferred for detecting cerebellopontine angle tumors and brainstem infarcts, and have replaced CT scans as the study of choice for these conditions 1. However, there may be situations where a CT scan is necessary, such as in patients with pacemakers, severe claustrophobia, or financial constraints, or in patients with known bone disease, such as Paget disease or fibrous dysplasia.

Some key points to consider when evaluating the use of CT scans in patients with SSNHL include:

• The potential risks of radiation exposure and side effects of intravenous contrast
• The lack of useful information provided by CT scans for initial management of SSNHL
• The preference for MRI scans in detecting cerebellopontine angle tumors and brainstem infarcts
• The possibility of using CT scans in certain situations, such as in patients with contraindications to MRI or known bone disease. As stated in the guideline, the history and physical examination would have determined whether a cholesteatoma or other pathologic condition was present, and if so, a targeted temporal bone CT would then be more appropriate 1.

From the Research

CT Scan of the Brain

• The first computed tomography (CT) scan was performed on a patient's brain in 1971 2.
• Clinical CT systems were introduced in 1974 and dedicated to head imaging only 2.
• CT scans of the brain are commonly used to assess ischemia and stroke, intracranial hemorrhage and trauma 2.
• CT angiography (CTA) has become the standard for first-line cerebrovascular evaluation 2.

Safety Concerns

• There is controversy surrounding the question of whether CT scans can lead to future cancers 3.
• The doses used in CT are higher than those used in conventional radiographic examinations, but still 10 to 100 times lower than the dose levels that have been reported to increase the risk of cancer 3.
• Radiation dose optimization should always be part of technical advancements in CT imaging 2.
• The risk of cancer from CT scans is still uncertain, but a meta-analysis found an increased risk of cancer with increased radiation dose and multiple CT scan sites 4.

Patient Anxiety

• Anxiety does not only occur before MRI but also before CT scans 5.
• Sources of anxiety include communication of CT results, administration of contrast agents, radiation exposure, and claustrophobia 5.
• Women seem to be more receptive to anxiety than men, with greater fears concerning examination results, radiation exposure, administration of contrast, and claustrophobia 5.

Pregnancy and CT Scans

• CT remains the most appropriate tool for initial rapid diagnosis of acute neurological conditions in pregnancy 6.
• Noncontrast MRI is generally considered safe in pregnancy, as no evidence of fetal adverse effects has been demonstrated to date 6.
• Iodinated CT contrast agents are likely safer than gadolinium-based MRI contrast agents because of gadolinium accumulation in the amniotic fluid and fetal tissue 6.