Neurocognitive disorders (NCDs) are conditions characterized by a decline in a person’s previously attained level of cognitive function. This decline is not a normal part of aging but represents a significant change in mental processes. NCDs are acquired deficits, meaning they develop after birth, typically resulting from brain pathology or injury. These conditions affect essential abilities like memory, perception, and problem-solving.
Defining the Spectrum: Major Versus Mild
NCDs are classified into Major Neurocognitive Disorder and Mild Neurocognitive Disorder. The factor differentiating them is the degree to which the cognitive decline interferes with a person’s independence in daily life.
Major Neurocognitive Disorder, which largely replaces the older term “dementia,” involves a substantial cognitive decline severe enough to significantly impair independence. Individuals with a major NCD require assistance with complex everyday activities, such as managing finances or medications. The measurable decline in cognitive performance is typically marked, often testing two or more standard deviations below the norm.
Mild Neurocognitive Disorder is diagnosed when there is a modest cognitive decline that has not yet compromised independence. While the individual may notice difficulties and require compensatory strategies, they can still complete daily tasks on their own. This milder form is important for early detection, as it can represent an earlier stage of a progressive disease process.
Core Cognitive Domains Affected
The decline associated with NCDs is assessed across six specific cognitive domains. Evaluating these domains helps clinicians determine the specific pattern of decline.
Complex Attention involves the ability to sustain, divide, or selectively focus attention. Impairment manifests as difficulty tracking multiple conversations or struggling to perform tasks in a busy environment.
Executive Function covers higher-level skills like planning, decision-making, working memory, and correcting errors. Decline may be seen in problems organizing a complex project or managing a budget.
Learning and Memory deficits include difficulty acquiring new information or recalling recent events, such as forgetting recent conversations. Language impairment involves trouble finding the right words (aphasia) or understanding spoken or written language.
The Perceptual-Motor domain relates to visual perception and coordinated movements, causing struggles with driving or using tools. Social Cognition involves recognizing emotions and understanding social cues, and a decline can lead to inappropriate comments or a reduced ability to read social situations.
Underlying Conditions Leading to Neurocognitive Decline
Neurocognitive disorders are not diseases themselves but are syndromes caused by a wide range of medical conditions, injuries, or illnesses.
The most common cause is Alzheimer’s disease, a neurodegenerative condition characterized by the buildup of abnormal protein plaques and tangles that cause neurons to die. This leads to an insidious onset and gradual progression of cognitive decline.
Vascular NCD results from cerebrovascular events like strokes or chronic reduced blood flow to the brain, which deprives tissue of oxygen and nutrients. This decline often progresses in a stepwise fashion, with sudden drops in function following new vascular incidents.
Traumatic Brain Injury (TBI) can cause an NCD immediately following the injury or years later. The mechanical force disrupts brain tissue and neuronal connections, causing an acquired cognitive deficit linked directly to the traumatic event.
Other causes include HIV infection, which leads to damage and inflammation in the central nervous system, and Parkinson’s disease, where the loss of dopamine-producing neurons in the brainstem can eventually affect cognitive function, memory, and attention. Substance or medication-induced NCDs result from prolonged, excessive use of drugs or alcohol, or as a side effect of certain prescription medications.
Identifying and Addressing Neurocognitive Disorders
Identifying an NCD begins with a comprehensive evaluation, including a clinical interview with the individual and a knowledgeable informant, such as a family member. Clinicians use cognitive screening tools to objectively measure the extent of decline across the cognitive domains.
A thorough medical workup rules out potentially reversible causes of cognitive change, such as thyroid problems, vitamin B-12 deficiency, or depression. It also identifies structural causes like tumors or strokes using brain imaging. Blood tests can detect metabolic or infectious issues contributing to the symptoms.
Management of NCDs focuses on maximizing function and improving quality of life, especially in the early stages. Non-pharmacological approaches include cognitive rehabilitation exercises to strengthen specific mental skills and environmental modifications to simplify daily routines. Support and education for caregivers are a central component of addressing the ongoing challenges.