Long-Term Manifestations of Stroke
Common Symptoms and Signs Related to Neuroanatomy
Stroke can be associated with permanent neurological changes and disability. The nature of the impairment depends on the location of the stroke in the brain.
Stroke is a condition of neurological change when part of the brain is deprived of its blood supply. This can occur with obstruction of blood flow (ischemic stroke) or bleeding out of the vessels (hemorrhagic stroke). Depending on how soon the problem is addressed, a patient may have full recovery or neurological impairment from irreversible brain injury with little recovery. The location of the stroke determines the type of impairment.
Motor and Sensory Deficits
Motor and sensory function involve two areas of the brain separated by a groove called the central sulcus. One is the motor cortex in charge of generating all voluntary muscular movements from head to toe. The other is the primary somatic sensory cortex allowing the person to sense pressure, temperature, and pain. The nerve pathways from both cortices cross to the other side so that the left side of the brain deals with motor and sensory functions for the right side of the body, and vice versa.
Stroke affecting these cortices or their pathways, whether a large stroke or a small deeper stroke (lacunar infarct), results in motor and sensory deficits in one side of the body, either partially or completely. Motor and sensory functions for the head, including the eyes and the throat, can also be affected by injury to the brain stem where the responsible cranial nerves originate. Such patients may require physical therapists to train in movements that get around physical limitations and to determine the need for wheelchairs and other special equipment. Additionally, occupational therapists can assist stroke patients with fine motor skills and activities of daily living, particularly when the arm is affected. If the ability to swallow has been impaired, speech therapists can help retrain the throat muscles and determine which foods are safe to swallow.
Language Impairment
In general, one hemisphere of the brain is considered more dominant than the other. About 95% of people who are right-handed have a dominant left cerebral hemisphere. The dominant hemisphere holds two key areas for language and communication. Broca's area is located below the motor cortex and enables one to form the words and sentences that are spoken or written. Wernicke's area, located a short distance from Broca's area towards the back of the brain, is responsible for understanding written and spoken language. The non-dominant hemisphere has areas corresponding to Broca's and Wernicke's areas that deal with rhythm and intonation (prosody) in expressive and receptive communication, respectively.
Stroke injury to Broca's area results in Broca's aphasia (a.k.a. expressive aphasia, motor aphasia, and nonfluent aphasia) in which the patient struggles to form clear sentences, often communicating one word at a time. Wernicke's aphasia (a.k.a receptive aphasia, sensory aphasia, and fluent aphasia) is characterized by difficulty with understanding language and communicating in a nonsensical way, although with grammatical structure relatively intact. For the nondominant hemisphere, injury to the corresponding areas result in the inability to express tone (motor dysprosody) or recognize tone in communication (sensory dysprosody).
Dementia
The frontmost portions of the brain perform the various cognitive functions, including concentration, judgment, and decision making. Stroke injury to these and other areas can impair cognition (vascular dementia or multi-infarct dementia) very much like other causes of dementia, such as Alzheimer's disease.
Final Words
The preceding is an overview of common stroke manifestations, serving as an introduction to neurological impairments from stroke rather than a complete list. In addition, several functions rely on multiple areas of the brain and a stroke involving one blood vessel territory essentially results in multiple impairments. The primary take-home message is that the brain is such an important organ that neurological deficits from stroke can be disabling and life-changing. Prevention with a healthy lifestyle continues to be an important measure.
References
- Sylvius Neuroanatomical Reference
- eMedicine - Stroke Motor Impairment
- eMedicine - Multi-infarct Dementia
