What does increased T2 (Transverse Relaxation Time) FLAIR (Fluid-Attenuated Inversion Recovery) signal in the bilateral globus pallidus indicate?

Increased T2 FLAIR Signal in the Bilateral Globus Pallidus: Differential Diagnosis and Clinical Significance

Increased T2 FLAIR signal in the bilateral globus pallidus is most likely an age-related physiological finding but can also indicate various pathological conditions requiring clinical correlation with patient symptoms, history, and additional imaging features. 1

Common Etiologies of Bilateral Globus Pallidus T2/FLAIR Hyperintensities

Physiological/Age-Related Changes

• Research shows that bilateral T2 hyperintensities in the medial part of the globus pallidus are common incidental findings, observed in nearly 30% of cases, with higher prevalence in elderly patients 1
• These changes correlate with age and are more common in patients with hypertension, dyslipidemia, and globus pallidus calcification 1

Pathological Causes

Toxic/Metabolic Conditions

• Carbon monoxide poisoning: Characteristic bilateral symmetric hyperintensities in the globus pallidus, caudate nuclei, putamen, and sometimes thalamus 2
• Hepatic encephalopathy: May show T2 hyperintensities in the globus pallidus, though T1 hyperintensity is more characteristic 3, 4
• Wilson's disease: Typically shows T2 hyperintensities in the basal ganglia, though atypical presentations with T1 hyperintensity have been reported 3
• Kernicterus: Usually presents with T1 hyperintensity in the globus pallidus, but may show T2 changes in later stages 5

Neurodegenerative Disorders

• Creutzfeldt-Jakob disease (CJD): May present with basal ganglia hyperintensities on T2/FLAIR sequences 6

Inflammatory/Immune-Mediated Conditions

• Amyloid-related imaging abnormalities (ARIA): Can present with T2/FLAIR hyperintensities in various brain regions including basal ganglia 7
• Multiple sclerosis: Rarely affects the globus pallidus but can present with T2/FLAIR hyperintensities throughout the brain 7

Infectious Etiologies

• Encephalitis: Various infectious encephalitides can present with T2/FLAIR hyperintensities in the basal ganglia 7
• Progressive multifocal leukoencephalopathy (PML): Though uncommon in the basal ganglia, PML can present with T2/FLAIR hyperintensities throughout the brain 7

Clinical Approach to Evaluation

Key Clinical Correlations to Consider

1. Age of the patient: In elderly patients, these findings are more likely to be incidental 1

2. Neurological symptoms:

   • Rapidly progressive dementia with myoclonus suggests CJD 6
   • Visual disturbances with basal ganglia involvement may suggest carbon monoxide poisoning 2
   • Movement disorders may suggest Wilson's disease or other metabolic disorders

3. Exposure history:

   • Recent carbon monoxide exposure
   • Medications (particularly amyloid-modifying therapies) 7
   • Hepatic disease history 3, 4

Additional Imaging Features to Evaluate

1. Pattern of involvement:

   • Bilateral symmetric involvement is typical for toxic/metabolic causes
   • Asymmetric or multifocal lesions may suggest inflammatory or infectious causes

2. Additional sequences:

   • T1-weighted images: Hyperintensity suggests manganese deposition (hepatic encephalopathy) or copper/iron deposition (Wilson's disease) 3, 4
   • Diffusion-weighted imaging (DWI): Restricted diffusion may suggest acute ischemia or CJD 7
   • Susceptibility-weighted imaging (SWI): Helpful for detecting iron deposition or microhemorrhages 7

3. Contrast enhancement patterns:

   • Enhancement suggests inflammation or infection 7
   • Lack of enhancement is more typical of metabolic or degenerative causes

Management Recommendations

1. For incidental findings in asymptomatic elderly patients:

   • Consider as likely age-related changes, especially if isolated to the medial globus pallidus 1
   • Evaluate for vascular risk factors (hypertension, dyslipidemia)
   • Consider follow-up imaging only if clinically indicated

2. For symptomatic patients:

   • Complete laboratory workup including liver function tests, copper studies, and inflammatory markers
   • Consider CSF analysis if infectious or inflammatory etiology is suspected 7
   • Follow-up imaging to assess progression

3. For patients on amyloid-modifying therapies:

   • Regular MRI monitoring is recommended, especially for patients with high JCV index values 7
   • Any new T2/FLAIR hyperintensities should prompt consideration of ARIA or PML 7

Pitfalls and Caveats

• Isolated bilateral globus pallidus T2/FLAIR hyperintensities in elderly patients are often incidental and physiological 1
• Always correlate with clinical symptoms before attributing to pathology
• Consider technical factors that may affect signal intensity (field strength, sequence parameters)
• Evaluate for additional signal abnormalities in other brain regions that may help narrow the differential diagnosis
• Remember that some conditions (like hepatic encephalopathy) classically show T1 hyperintensity rather than T2/FLAIR hyperintensity in the globus pallidus 3, 4

By systematically evaluating the clinical context, additional imaging features, and laboratory findings, the significance of increased T2/FLAIR signal in the bilateral globus pallidus can be appropriately determined and managed.