Blown Away: The effects of noise and blast injuries on our troops. Objectives. Threshold shifts. Detection of sound. Tank Gunner

Transcription

1 Blown Away: The effects of noise and blast injuries on our troops James V. Crawford, MD Objectives Examine the challenges presented by hearing loss on soldiers in battle Compare the hearing protection options available to our soldiers Identify the unique injuries IED exposure causes in warfighters Describe the methods being used to diagnose blast injuries and mild traumatic brain injury (TBI) Analyze the difference between types of TBI Discuss treatments that have been and are being developed for blast injured soldiers Participate in an interactive discussion of blast injury Threshold shifts Sense of hearing is the main survival resource of the dismounted soldier Detection of sound Normal voice Normal hearing (H-1): 32m Moderate SNHL (H-2): 100m Moderate SNHL with TTS (H-3): 180m Footsteps in leaves Normal hearing (H-1): 0.6m Moderate SNHL (H-2): 5.5m Moderate SNHL with TTS (H-3): 100m Rifle bolt closing Normal hearing (H-1): 46m Moderate SNHL (H-2): 210m Moderate SNHL with TTS (H-3):1000m Tank Gunner Word intelligibility Time to identify target Incorrect command heard by gunner Correct target identification Enemy targets killed Wrong target shot Tank crew killed by enemy Good 40 sec 1% 98% 94% 0% 7% Poor 90 sec 37% 68% 41% 8% 28% Site Hearing loss after training exercise w/ hearing protection Marines Infantry Pendleton Army Special Forces Israeli Basic Trainees Conditions 3-5 days M-16 Standard hearing protection 3 days Small arms & heavy weapons Double hearing protection 56 days M-16 Hearing protection Study Size Hearing Loss 11% 11% 10% Investigators Wolgemuth et al., 1998 Vause, 1994 Attias et al.,

2 Ft Lewis STS rates by MOS: 03 MOS SF Assist Ops/Intel Sgt 18F FA Targeting Technician 131A M1 Armor Crewman 19K SF Medical Sergeant 18D SF Communications Sgt 18C Medical Specialist 91W Infantryman 11B Cavalry Scout 19D All personnel # tested % with STS 50% 50% 31% 26% 22% 21% 19% 19% 18% Sound Pressure Level in db Tank F-15 Fighter Claymore Mine Grenade Launcher M16 Rifle 50 Cal Machine Gun Semi-automatic Pistol Hand Grenade Mortar, 81mm Howitzer RPG mm SPL of Weapon Attenuated Weapon (-14dB) Time-weighted threshold for damage Impulse threshold for damage TOW Missile M67-90mm M40A2/A1-106mm Costly problem Fourth most common military disability 22,000 new claims/year Annual cost to government: $1 billion Current protection Insert ear plugs 25 to 30 db attenuation (if properly fitted) Over ear muffs 40 to 45 db attenuation Don t work with kevlar Active hearing protection Current protection Chemical protective agents N-acytelcystine Other free radical scavengers Why worry about blasts? Balance disorders are present alone or in combination with other injuries in 65% of the injuries in Southwest Asia Over 70% of individuals involved in significant blast injuries have a resultant balance disorder Almost all individuals suffering a closed head injury in Iraq have a resultant balance disorder A significant number of individuals with multiple blast exposures but no other injury will present with balance disorders 2

3 So what? Over 50% of balance disorders in the civilian population will resolve over time Less than 20% of war injured balance disorders will resolve without treatment Untreated balance disorders Directly costs the military over $750 Million dollars a year in lost equipment and in lost mission accomplishment per year Result in medical discharges of valuable human resources (often at the peak of their military career) Cost billions of dollars a year in re-training and medical benefits Strain an already tight personnel pipeline Have dramatic effects on the lives of those who suffer from the balance disorder Traumatic Brain Injury- Civilian Issues Second most common neurological disorder Incidence of over 500/100,000 individuals Costs the United States over $40 billion/year Pathophysiology Closed Head Injury (CHI) Consequences of head injury Diffuse Axonal Injury (DAI) Focal Edema Release of excitatory neurotransmitters Resultant CNS effects CHI Altered/disturbed message transfer along balance pathway Altered vestibular reflexes (VOR, COR, etc.) Apoptotic cell death (continuing long after injury) Pathophysiology Blast Injury Shock wave effect Sheer injury in vestibular end organ Oxidative cellular stress Release of excitatory neurotransmitters Direct stimulation of apoptotic pathways 3

4 Resultant CNS effect Blast Injury Targeted injury pattern - but may be at multiple sites Some Peripheral end organ damage is usually present which may be bilateral Hearing loss/tinnitus often present Distinct pattern of cognitive difficulty Multi-systems Trauma in modern war Body armor allows individuals to survive more significant impacts and injuries Associated injuries that effect balance Orthopedic legs Spine injuries Cognitive injuries MRAPs help survival, but not blasts Work-up Specialized vestibular history and physical Characterization of injury Standard history questions Otolaryngologic and Neurologic Physical exam Evaluation by a physician Evaluation captured in a computer program (AHLTA) Evaluation - continued Audiogram Neuro-vestibular testing Standardized assessment instruments MRI scan Neuro-vestibular testing Dynamic Computerized Posturography Rotational chair testing of gain, phase, and symmetry Step-velocity testing to determine the vestibular time constant High speed head rotation testing for gain Standardized Assessment Instruments Dynamic Gait Index (DGI) Dizziness Handicap Index (DHI) Activity-Specific Balance Confidence Scale (ABC) Vestibular activities of daily living (VADL) Balance Error Scoring System (BESS) 4

5 Classification of primary blunt trauma Entity Positional Vertigo History Positional Vertigo Physical Exam Nystagmus on Dix -Hallpike test or modifieddix -Hallpike test Vestibular Tests No other abnormalities Four Groups Post-traumatic positional vertigo Post-traumatic exertional dizziness Post-traumatic migraine associated dizziness (PTMAD) Post-traumatic spatial disorientation Exertional Dizziness Migraine Associated Dizziness Spatial Disorientation Dizziness during and right after exercise Episodic Vertigo with periods of unsteadiness Headaches Constant feeling of unsteadiness worsened by standing but still present when sitting or lying down Drifting to one side while walking Shifting weight when standing still Abnormalities in challenged gait testing Abnormalities in challenged gait testing +/-Abnormalities on head impulse testing Normal static posture tests Abnormalities on standard gait tests +/- Abnormalities on head impulse testing Abnormalities on static posture tests No other abnormalities VOR gain, phase, or symmetry abnormalities High frequency VOR abnormalities Normal posturography VOR gain, phase, or symmetry abnormalities High frequency VOR abnormalities Abnormal posturography Central findings on rotation chair testing Classes of TBI Mild Mild Head injury, GCS 13-15, No or transient LOC. Moderate Moderate head injury, GCS 9-13, and no need for ICP monitor or ventilator (due to head injury) Severe Severe head injury, GCS <8 and/or need for ICP monitor, and or need for ventilator support due to head injury NMCSD/NMRC Study CHI study Patients with only blunt trauma Hoffer ME, Gottshall KR, Moore RJ, Balough BJ, Wester DC. Characterizing and Treating Dizziness after Mild Head Trauma. Otol/Neurotol, 25(2);135-38, 2004 Hoffer ME, Balough BJ, Gottshall KR. Posttraumatic Balance Disorders. Int. Tin J. 13(1):69-72, 2007 Materials and Methods Active duty military individuals with TBI Combat MVA Altercation Sporting event Exclusion criteria Temporal bone fracture Significant visual or proprioceptive damage Seen in clinic more than 6 weeks post accident Patients 198 Total Patients Assigned by two independent investigators Mild - 75% Moderate 13% Severe 12% Moderate and severe patient numbers limited by eligibility requirements for study 5

6 Dizziness Types 100 BPV 90 Exercise Distribution of Dizziness Types Percentage of Patients PTMAD Disorientation 27% 26% 8% BPV Exercise PTMAD Disorientation 10 0 Mild Moderate Severe 39% Outcome data All patients underwent vestibular rehabilitation All migraine patients received medicines Migraine prophylactic medicine (Verapamil or Topiramate) Migraine abortive medicine (Triptin) Percent of Patients 100 VOR Abnormalities 8 week follow-up PTMAD Spatial Disorientation Pre-treatment Post-treatment Functional Outcome Findings Weeks RTW Symptoms Resolution BPV Exertional PTMAD Disorientation Vestibular functional outcome not dependent on injury severity Vestibular functional outcome dependent on dizziness class More severe CHI does worse because more likely to be in worse dizziness class 6

7 Recovery Rates 73% of our patients (positional, exertional, and PTMAD groups) respond in 1-8 weeks indicating a possible positive effect of vestibular rehabilitation and active treatment in these three groups Over 85% of patients returned to full duty status (many have returned to Iraq) Blast Induced - TBI Slightly different set of diagnoses More Cognitive difficulty Higher degree of hearing loss Blast Induced Dizziness Entity Positional Vertigo Exertional Dizziness Blast induced Disequilibrium Blast induced Disequilibrium with Vertigo History Positional Vertigo Dizziness during and right after exercise Constant feeling of unsteadiness when standing and waling worse with challenging environments Constant Headache Constant feeling of unsteadiness when standing and waling worse with challenging environments Constant Headache Episodic Vertigo Physical Exam Nystagmus on Dix - Hallpike test or modified Dix -Hallpike test Abnormalities in challenged gait test Abnormalities in challenged gait Abnormalities in tandem Romberg Abnormalities with quick head motion Abnormalities in challenged gait Abnormalities in tandem Romberg Abnormalities with quick head motion Vestibular Tests No other abnormalities No other abnormalities Abnormal posturography Abnormal target acquisition, dynamic visual acuity, and gaze stabilization +/- VOR gain, phase, or Abnormal symmetry abnormalities posturography Abnormal target acquisition, dynamic visual acuity, and gaze stabilization VOR gain, phase, or symmetry abnormalities Unresolved Issues Blast injury vestibular frequency distribution Blast injury response to therapy (very good but how very good?) Characterization of mixed injury pattern patients (like CHI, like Blast, or something different) Vestibular Rehabilitation Treatments that allow individuals to adapt to, compensate for, or respond to a balance disorder Vestibular Rehabilitation Therapeutic exercises Therapeutic maneuvers Physical Conditioning Coping skills Devices 7

8 Theory behind Vestibular Rehabilitation The balance system is governed by a complex set of inputs Inner ears, eyes, proprioception Non-traditional vestibular inputs Ultimately these inputs must be integrated at the level of the brainstem or cerebellum Finally, the inputs need to be analyzed and acted upon at the reflex or cortical level Theory behind Vestibular Rehabilitation Complex arrangement allows for multiple sites at which to impact system Most of the sites (even the CNS sites) have two important characteristics Redundancy Plasticity Sites at which to intervene Vestibular-ocular Reflex (Head and eye interaction) Vestibular-spinal Reflex (Head and spine interaction) Posture spatial orientation sense Gait with and without tasks General Conditioning Getting in shape Going forward Hearing and balance must be accurately screened early in the field Portable audiometers are being deployed at far forward sites BAS level vestibular assessment under discussion DHI Platform Specifically designed instrument/test Going forward Standard Operating Procedures (SOP) must be developed for specific balance disorders Options Treat/Observe in field Medivac must be to a definitive center ASAP (preliminary data analysis shows earlier definitive vestibular treatment shortens recovery time and improves outcomes) Going forward Network of head injury centers must be created with a significant vestibular element Vestibular and hearing care must be recognized as a vital component Information and techniques Computerized Sharable (HIPPA Protection) Studiable Effort must be tri-service and joint 8

9 Conclusion Post-traumatic dizziness is a significant military issue Dizziness seen in combat may be very different than traditional trauma centers see in CONUS Emerging volume of documented, peer-reviewed work validating the impact of treatment We must move forward on battlefield efforts to treat individuals earlier We must move forward on CONUS efforts and create dedicated centers 9