CMSD 642 Neuropathologies of Swallowing and Speech
California State University, Chico
Patrick McCaffrey, Ph.D
Chapter 2: Causes and Incidence: Traumatic Brain Injury (TBI)
According to Adamovich, Henderson, and Auerbach, (1984) as many
as 400,000 head injuries occur in the United States each year. The
severity of head injury has generally been classified as mild,
moderate and severe. Mild head injury has been defined as
concussion, while severe head injury means being in a coma for at
least six hours. There does not appear to be a consensus for a
definition of moderate head injury. Jennett and Teasdale developed
the Glasgow Coma Scale in 1974 (Bach-y-Rita, 1989). It is a
numerical scale that quantifies level of consciousness in response
to three categories: response to pain, ability to open eyes, and
ability to speak.
Types of Brain Injury (Urosevich, 1984)
1. Epidural Hematoma
Bleeding occurs above the dura mater, usually from meningeal arteries. The blood quickly accumulates, creating a space between the skull and the dura. The typical course for the patient is instantaneous loss of consciousness followed by a short period of lucidity, then a lapse into unconsciousness. The hematoma frequently exerts pressure on cranial nerves which can result in ipsalateral lower motor neuron paralysis. Because cranial nerves innervate muscles of swallowing and speech as well as those for eye movement, the paralysis can result in unilateral pupillary dilation and paralysis of the jaw, face, throat, larynx, or tongue.
2. Subdural Hematoma
Bleeding occurs into the potential space below the dura mater and above the arachnoid mater. It is typically venous and found above the frontal and temporal cerebral lobes. Since the primary and association motor cortices as well as pre-frontal cortex are in the frontal lobes damage there can result in swallowing, speech, language or cognitive problems. It is common for the appearance of symptoms to be delayed for several days or a week or more. A coma or less severe symptoms may develop. The latter include: seizures, unilateral or bilateral weakness or paralysis.
3. Intracerebral Bleeding
Bleeding is within the cerebrum and often includes sub-cortical structures. It most often occurs because of penetrating head wounds. The frontal and temporal lobes are frequently involved. Of course this type of injury could occur anywhere in the brain. Dysphagia, aphasia, apraxia, dysarthria, paralysis, as well as visual and other problems can occur.
4. Tentorial Herniation
Edema of the brain which occurs due to TBI, forces neural tissue through the tentorial notch between the cerebrum and cerebellum. This results in the squeezing of the brain stem (mid brain, pons, medulla). The cranial nerves are affected resulting in dysphagia, and speech problems, or even in death, as the medulla is important to respiration and circulation. Some of the initial symptoms of tentorial herniation are weakness, paralysis (often on one side), and visual disturbances (pupillary dilation, double vision). Respiration may be affected, the heart may be quite slow (bradycardia), or decortication (removal of cortical tissue) may be necessary.
5. Sites of lesion for traumatic brain injury
They are usually in the frontal or temporal lobe. If there is acceleration-deceleration injury with rotational trauma it can cause shearing of axons often resulting in dysarthria.
Copyright, 1998-2011. Patrick McCaffrey, Ph.D. This page is freely distributable.