Presumptive Cerebral Microbleeds in Dogs: A Common Yet Underrecognized Finding in Aging Canines

With advances in veterinary medicine and improved pet care, dogs are living longer than ever before. As the canine population ages, age-associated neurological changes—once rarely diagnosed—are now more frequently encountered on brain imaging. One such change is presumptive cerebral microbleeds (pCMBs), an MRI finding increasingly recognized in elderly dogs.

A large retrospective study published in PLOS ONE (2025) analyzed the prevalence and distribution of pCMBs in 747 dogs undergoing brain MRI. The results show that pCMBs are a common, age-associated finding, particularly in small-breed and female dogs, and are often associated with brain atrophy.

What Are Cerebral Microbleeds?

Cerebral microbleeds are small, round or ovoid areas of signal void on T2-weighted MRI sequences*, believed to represent the leakage of blood products into the brain tissue. In humans, these lesions are associated with vascular aging, cognitive decline, and increased stroke risk.

In dogs, however, data have been limited. This study helps define the epidemiology and imaging characteristics of pCMBs in a veterinary context, aiding clinicians in interpreting incidental or symptomatic MRI findings.

Study Highlights

• Sample size: 747 dogs (all underwent 1.5T MRI with T2* sequences)

• Prevalence of pCMBs: 142 dogs (19%)

• Age distribution:

  • 96.5% of dogs with pCMBs were over 9 years old

  • Dogs ≥10 years had the highest prevalence (p < 0.001)

• Breed size:

  • Small breeds were significantly more affected

  • Most common breeds with pCMBs: French Bulldogs, Yorkshire Terriers, Poodles

• Sex distribution:

  • Female dogs were more likely to have pCMBs than males

• Lesion distribution:

  • Most dogs had multiple lesions (62%)

  • Lesions were predominantly lobar (57.7%)

• Concurrent changes:

  • Brain atrophy was present in 61.3% of pCMB-positive dogs

Imaging and Diagnostic Considerations

T2-weighted GRE sequences* were essential for detecting pCMBs. Lesions were defined as:

• ≤5.7 mm in diameter

• Signal voids with blooming artifact

• Surrounded by normal brain parenchyma

• Absent of T1 or T2 hyperintensity

• Not associated with trauma

These features are consistent with published criteria in both veterinary and human radiology literature. Notably, without histopathologic confirmation, the term “presumptive” is used.

Clinical Implications

1. Common and Often Incidental

Many pCMBs were found in asymptomatic dogs or those undergoing MRI for unrelated reasons. Like in human medicine, these lesions may often be incidental—though their clinical significance is still being investigated.

2. Associated with Brain Aging

The strong correlation with age and brain atrophy suggests that pCMBs may be a normal part of canine brain aging, particularly in small breeds.

3. Importance of T2 Sequences*

This study underscores the value of including T2-GRE or SWI sequences* in routine MRI protocols, especially in dogs over 9 years old. Without them, pCMBs would likely go undetected.

4. Possible Neurological Relevance

While not all dogs with pCMBs show signs of neurological disease, some prior studies have linked these lesions to shortened survival times, cognitive decline, or vascular events. This study did not assess outcomes directly, but it supports further research in this area.

Takeaways for Veterinary Practitioners

• Expect to see pCMBs more frequently in aging dogs, especially small breeds and females.

• Interpret with context: The presence of pCMBs doesn’t always indicate disease. Evaluate clinical signs and other MRI findings (e.g., atrophy, leukoaraiosis) when making decisions.

• Use complete MRI protocols, including T2*, for geriatric patients with neurologic signs—or even for baseline imaging in older dogs.

• Educate clients that age-related changes like pCMBs may not require treatment, but awareness helps manage expectations and monitoring.

Presumptive cerebral microbleeds are not rare. They are a common, MRI-visible manifestation of cerebral aging in dogs, particularly in small-breed and elderly patients. Their identification should prompt a comprehensive evaluation for concurrent age-related changes, such as brain atrophy, but not necessarily alarm—especially in clinically normal animals.

As the veterinary field increasingly embraces advanced imaging, recognizing and interpreting pCMBs accurately will be important for both diagnostics and client communication. Future research will help clarify their pathophysiology and clinical consequences.

Full Citation:
Coelho CMM, Brock GW, Ferraz Barros RA, et al. (2025) Prevalence and epidemiology of presumptive cerebral microbleeds in a population of 747 dogs undergoing brain MRI: a retrospective study. PLoS One 20(10): e0332658. https://doi.org/10.1371/journal.pone.0332658