Periventricular lesions are changes in the brain that appear on imaging scans, primarily Magnetic Resonance Imaging (MRI). While the term may sound alarming, these lesions are not always indicative of severe disease, with some considered normal with aging. Their presence can be associated with a range of conditions, some more concerning than others. Understanding these findings requires careful consideration of their nature, location, and the broader clinical picture.
Understanding Periventricular Lesions
Periventricular lesions are altered brain tissue found around the brain’s ventricles, fluid-filled spaces deep within the brain. Detected primarily through MRI scans, they appear as bright or white spots, known as white matter hyperintensities, on sequences like T2-weighted and Fluid-Attenuated Inversion Recovery (FLAIR) images. The FLAIR sequence is useful as it suppresses cerebrospinal fluid signal, making lesions near the ventricular margins more distinct. These bright spots indicate regions where the white matter, the brain’s communication network, has undergone changes or damage.
They signify a disruption in the normal structure or connectivity of brain tissue, often due to myelin sheath damage. Periventricular lesions are defined as T2-hyperintense white matter lesions in direct contact with the lateral ventricles, without normal white matter in between. Lesions touching the ventricles and located in the corpus callosum, a large bundle of nerve fibers connecting the brain’s hemispheres, are also included.
Conditions Associated with Periventricular Lesions
Periventricular lesions are commonly observed in several neurological conditions, each with distinct implications. In Multiple Sclerosis (MS), these lesions are a characteristic feature and play a role in diagnosis, often appearing ovoid and perpendicular to the ventricles, sometimes referred to as “Dawson’s fingers”. The presence of three or more periventricular lesions can support the diagnosis of MS by demonstrating dissemination in space, a key diagnostic criterion. However, a single periventricular lesion may not be specific enough for an MS diagnosis.
Cerebrovascular disease, including silent strokes or chronic ischemia, is another common cause of periventricular lesions. These lesions often reflect small vessel disease, where tiny blood vessels in the brain are damaged, leading to reduced blood flow and tissue changes. Such changes can be associated with risk factors like high blood pressure, diabetes, high cholesterol, and smoking. Periventricular lesions linked to small vessel disease may appear more diffuse or irregular compared to those seen in MS.
Migraine also shows an increased prevalence of white matter lesions, including those in the periventricular region, although their exact cause remains unclear. These lesions are typically small, punctate hyperintensities, and while more common in people with aura, they are generally not associated with significant neurological issues or cognitive decline.
Periventricular lesions are a common finding in older adults and can be considered a normal part of the aging process, often termed “white matter hyperintensities of aging”. Their volume and number tend to increase with age, with periventricular lesions showing a more pronounced increase per decade compared to deep white matter lesions. In the elderly, these lesions may result from chronic hypoperfusion or changes in small blood vessels.
Clinical Manifestations of Periventricular Lesions
The presence of periventricular lesions does not always lead to noticeable symptoms, and their clinical impact varies significantly depending on the underlying cause, size, and specific location within the brain. In individuals with MS, periventricular lesions can contribute to a range of symptoms, including cognitive impairment, particularly affecting information processing speed and executive function. Other potential symptoms include fatigue, motor difficulties like weakness and spasticity, sensory disturbances such as numbness or tingling, and problems with vision.
When associated with cerebrovascular disease or aging, periventricular lesions can lead to more subtle and gradual symptoms. These may include cognitive changes, such as issues with memory or slower cognitive processing, and difficulties with balance and gait, potentially increasing the risk of falls. Mood changes, including depression, and urinary incontinence are also possible symptoms linked to white matter lesions. A quick onset and progression of these symptoms might be more concerning than gradual changes.
Distinguishing Periventricular Lesions
Differentiating the cause of periventricular lesions is a complex diagnostic challenge requiring a comprehensive approach by medical professionals, typically neurologists. Doctors consider a patient’s age, clinical symptoms, and the specific characteristics of the lesions on MRI scans. For instance, MS lesions often have a distinctive ovoid shape and are oriented perpendicularly to the lateral ventricles, sometimes referred to as “Dawson’s fingers”. In contrast, age-related white matter changes may appear as “periventricular capping” or more diffuse, less defined areas.
The location of lesions on MRI also provides clues; while periventricular lesions are common in MS, other areas like juxtacortical, infratentorial, and spinal cord lesions are also typical in MS. For cerebrovascular disease, lesions may be more diffuse or found alongside other signs of small vessel damage like lacunar infarcts or microbleeds. Migraine-related lesions, while often periventricular, are usually smaller than 3 mm and punctate, and tend to be more common in the frontal lobe. Interpretation of these imaging findings, combined with a detailed patient history and neurological examination, helps differentiate between various underlying conditions.