Blows and sudden jerks tend to cause lin­ear forces, in which the brain moves in a straight line in­side the skull. How­ever, some in­juries to the head cause ro­ta­tional forces within the brain.

EQUUS - - Tack& Gear -

Trau­matic brain in­juries (TBIs) are de­fined by the Cen­ters for Dis­ease Con­trol as jolts, blows or pen­e­trat­ing in­juries to the head that al­ter the vic­tim’s men­tal state. Although most of us un­der­stand that a sudden blow can cause a con­cus­sion, it’s im­por­tant to know that you don’t need to strike your head to sus­tain a dan­ger­ous brain in­jury: Sim­ply whip­ping your head hard can cause the brain---which floats in a layer of cere­brospinal fluid--to slam into the in­te­rior of the skull, and both a blow and a jolt can stretch, tear and/or bruise the neu­ral tis­sue.

The di­rec­tion of force mat­ters, too. Blows and sudden jerks tend to cause lin­ear forces, in which the brain moves in a straight line in­side the skull. How­ever, some in­juries to the head cause ro­ta­tional forces within the brain. “Ro­ta­tory move­ment is prob­a­bly more dan­ger­ous be­cause the brain can shift more and there’s twist­ing and tear­ing of fibers,” says Ju­lian Bailes, MD, chair­man of the Depart­ment of Neu­ro­surgery and co-di­rec­tor of NorthShore Univer­sity HealthSys­tem’s Neu­ro­log­i­cal In­sti­tute in Chicago. The sever­ity of TBIs can be ranked on dif­fer­ent of­fi­cial med­i­cal scor­ing sys­tems, such as the Glas­gow Coma Scale or the Ab­bre­vi­ated In­jury Scale, but gen­er­ally con­cus­sions can be de­scribed as mild, moder­ate or se­vere. To some de­gree, all TBIs can change the way a per­son thinks, feels and acts; they can also af­fect lan­guage and cause sleep dis­tur­bances. Peo­ple who sus­tain mild TBIs may lose con­scious­ness for a few min­utes, or they may re­main awake but sim­ply be con­fused or “dazed” fol­low­ing an in­jury. They may ex­pe­ri­ence mem­ory loss that per­sists for up to a day. Other symp­toms com­mon fol­low­ing milder TBIs in­clude fa­tigue, headaches, dizzi­ness, blurred vi­sion, nausea or vom­it­ing, loss of bal­ance, in­creased

ir­ri­tabil­ity or other emo­tional dis­tur­bances, sen­si­tiv­ity to bright lights or loud noises, ring­ing in the ears, and de­pres­sion. Some­times these signs can be sub­tle and easy to miss, and they may per­sist for weeks or in some cases symp­toms may last for a year or more.

Although re­cov­ery from mild TBIs is usu­ally un­event­ful, it can take a min­i­mum of six weeks for the neu­ral tis­sues to fully heal. Dur­ing that time, dam­age from an ad­di­tional blow to the head would be cu­mu­la­tive: A sec­ond TBI might cause se­ri­ous long-term com­pli­ca­tions or prove fa­tal, even if nei­ther blow alone would have been life-threat­en­ing. (For that rea­son, physi­cians sug­gest not riding or par­tic­i­pat­ing in other high-risk sports un­til the brain has had time to heal.)

More moder­ate to se­vere TBIs cause un­con­scious­ness for 30 min­utes or longer, rang­ing up to coma, and when awake, these pa­tients may ex­pe­ri­ence ex­ten­sive mem­ory loss. The pe­riod of un­con­scious­ness is a sign of much more se­ri­ous in­jury. “If a per­son is knocked un­con­scious, it usu­ally means their brain ex­pe­ri­enced enough strain to dis­rupt trans­mis­sion path­ways. A loss of con­scious­ness typ­i­cally means the head im­pact was more se­vere than when the symp­toms are a headache and dizzi­ness,” says biome­chan­i­cal en­gi­neer Stephanie Bonin, PhD, PE, of MEA Foren­sic En­gi­neers & Sci­en­tists in La­guna Hills, California.

These pa­tients al­most al­ways need to be hos­pi­tal­ized, pos­si­bly in in­ten­sive care. Blows to the head hard enough to cause se­ri­ous TBIs may also be com­pli­cated by is­sues such as skull frac­tures, hem­or­rhage or sub­du­ral hematoma (the pool­ing of blood be­tween the brain and the skull), all of which can place pres­sure on the brain and cause seizures, breath­ing dif­fi­cul­ties and other lifethreat­en­ing con­di­tions.

Peo­ple who sur­vive moder­ate and se­vere TBIs are likely to re­quire ex­ten­sive re­ha­bil­i­ta­tion. Long-term ef­fects are com­mon and may in­clude:

phys^cal chan\Zs! such as chron^c pain, seizures, loss of bowel or blad­der con­trol, and sleep dis­or­ders

co\n^t^vZ chan\Zs! ^nclud" ing dif­fi­cul­ties with mem­ory and con­cen­tra­tion

spZZch and lan\ua\Z ^mpa^r" ments, such as slur­ring, and dif­fi­cul­ties with read­ing, writ­ing and com­pre­hen­sion

sZn­sory ^ssuZs! such as lost or d^" min­ished taste or smell, blurred vi­sion or blind­ness, or ring­ing in the ears

Zmot^onal chan\Zs! such as a\" gres­sion, ir­ri­tabil­ity, lack of mo­ti­va­tion or de­pres­sion.

Over the long term, TBI---even a mild one---may leave a per­son at an in­creased risk for de­vel­op­ing epilepsy, Parkin­son’s dis­ease, Alzheimer’s dis­ease and other neu­ro­log­i­cal dis­or­ders.

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