Traumatic brain injury, or TBI, is a term used to describe physical damage to your brain which results in temporary or permanent impairment in neurological function. Approximately 1.4 million people in the United States experience significant head injuries each year. About 80,000 of them have permanent disability. According to experts at Evans Army Community Hospital at Fort Carson, Colorado, more than 20 percent of the soldiers evacuated from Iraq and Afghanistan have had some form of TBI. Potential complications of TBIs include seizures; amnesia; headaches; problems with hearing, vision or smell; behavioral changes; decreased intellectual function; and pituitary malfunction.
Seizures
Your brain is a biological computer driven by electrical signals that allow both internal integration and communication with your peripheral nervous system. Just like mechanical computers, your brain's activity can become disorganized -- "short circuited" -- because of inappropriate discharge of electronic impulses. Brain injury, with its subsequent inflammation and scarring, creates regions of heightened, disorganized electrical activity that occasionally escapes to the rest of your brain. Generalized disorganization of the brain's electrical activity manifests as a seizure.
Pituitary Injury
Your pituitary gland, a small structure suspended from the base of your brain, is housed within a bony hollow called the sella turcica, meaning "Turkish saddle." This bony enclosure usually offers good protection for your pituitary, which secretes a number of hormones involved in growth, metabolism, sexual function, fertility and fluid and electrolyte balance. Certain types of head trauma, such as fractures of the skull's base, can injure your pituitary and cause abnormalities in hormone production, resulting in a wide array of physiologic abnormalities, including low sodium.
Hyponatremia
Under normal circumstances, a pituitary hormone called antidiuretic hormone, or ADH, helps to control the amount of water your kidneys retain. When you are dehydrated, your pituitary secretes more ADH, leading to the reabsorption of water. When you consume more fluids, ADH secretion falls, and your kidneys release water. Pituitary injury can trigger the uncontrolled release of ADH, leading to inappropriate retention of water and dilution of the electrolytes in your bloodstream. Hyponatremia, meaning "low blood sodium," is one complication of head injury. According to "The Merck Manual of Diagnosis and Therapy," hyponatremia itself can be severe enough to trigger seizures.
Considerations
Head injury can be associated with a variety of complications. Seizures resulting from brain trauma often decrease in frequency as time passes, but they can be permanent, requiring medications for treatment. Inappropriate release of ADH from your pituitary also tends to improve with time, but water restriction and medications may be required either temporarily or for the long term to help maintain normal sodium levels. If seizures are caused by severe hyponatremia, emergency treatment is required to correct your sodium level and prevent permanent brain damage or even death.
References
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Traumatic Brain Injury"; Mark H. Beers, M.D., Editor-in-Chief; 2006
- "Journal of Head Trauma Rehabilitation"; Traumatic Brain Injury Screening: Preliminary Findings in a U.S. Army Brigade Combat Team; H. Terrio, et al.; Jan-Feb 2009
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Hyponatremia"; Mark H. Beers, M.D., Editor-in-Chief; 2006
