What conditions typically do not present with visible lesions on standard brain imaging, such as Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans?

Conditions That Typically Don't Present with Visible Brain Lesions on Imaging

Several neurological and psychiatric conditions typically do not present with visible lesions on standard brain imaging such as MRI or CT scans, making clinical evaluation and other diagnostic methods essential for diagnosis.

Functional Neurological Disorders

• Functional neurological disorders (conversion disorders) typically show normal brain imaging despite significant neurological symptoms 1
• These conditions present with neurological symptoms that cannot be explained by structural abnormalities visible on standard neuroimaging 1
• Symptoms may include weakness, sensory changes, or movement disorders without corresponding lesions 1

Psychiatric Conditions

• Most primary psychiatric disorders including depression, anxiety disorders, schizophrenia, and bipolar disorder typically show no specific lesions on standard brain imaging 1
• Brain CT scans in patients with psychiatric presentations and no focal neurologic findings have shown abnormalities in only about 5% of cases, with most being clinically irrelevant 1
• Routine diagnostic testing in psychiatric patients is generally low-yield and unlikely to affect management when patients are clinically stable 1

Headache Disorders

• Primary headache disorders (migraine, tension-type headache, cluster headache) typically present with normal neuroimaging 1
• Guidelines recommend that neuroimaging is not usually warranted for patients with migraine and normal neurological examination 1
• Data from patients with chronic headache provide enough reassurance that imaging will almost always be unnecessary if the history is consistent with tension-type headache and the neurological examination is normal 1

Neurodegenerative Conditions (Early Stages)

• Early stages of neurodegenerative diseases like Alzheimer's disease may not show visible structural changes on conventional imaging 1
• In early Alzheimer's disease, standard MRI or CT may appear normal before significant atrophy develops 1
• Advanced methods like volumetric MRI, amyloid PET, and FDG-PET may detect changes not visible on standard structural imaging 1

Seizure Disorders

• Many epilepsy syndromes, particularly idiopathic/genetic generalized epilepsies, often show no structural abnormalities on brain imaging 1
• In a retrospective review of patients with seizures, up to 44% had no identifiable etiology on imaging 1
• Metabolic causes of seizures (like hypoglycemia, hyponatremia) would not show as lesions on brain imaging 1

Mild Traumatic Brain Injury/Concussion

• Concussions typically do not show visible lesions on standard CT or conventional MRI 1, 2
• The American Congress of Rehabilitation Medicine notes that in mild TBI, neuroimaging is often normal or not clinically indicated 2
• Functional or microstructural changes may be present but require specialized imaging techniques not used in routine clinical practice 1

Cerebral Visual Impairment (Some Cases)

• Some cases of cerebral visual impairment, particularly those with subtle white matter abnormalities, may not show visible lesions on standard imaging 3
• More specialized techniques like OCT (optical coherence tomography) may show objective signs of trans-synaptic degeneration not visible on standard imaging 3

Diagnostic Challenges and Pitfalls

• Absence of visible lesions on imaging does not rule out neurological disease 4
• Clinical neurological tests vary considerably in their ability to detect radiologically demonstrated structural brain lesions 4
• MRI is generally more sensitive than CT for detecting subtle abnormalities, particularly for chronic intracerebral hemorrhage and microbleeds 5
• False negative studies may provide inappropriate reassurance when clinical suspicion is high despite normal imaging 1

When to Consider Advanced Imaging

• When standard imaging is normal but clinical suspicion remains high, consider:
  • More specialized MRI sequences (diffusion tensor imaging, functional MRI) 1, 3
  • Nuclear medicine studies (PET, SPECT) for metabolic or perfusion abnormalities 1
  • Repeat imaging after an appropriate interval if symptoms persist or progress 1