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Original

Dizziness after traumatic brain injury: Overview and measurement in the clinical setting

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Pages 293-305 | Received 17 Feb 2005, Accepted 20 Sep 2005, Published online: 03 Jul 2009

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I. Kleffelgaard, B. Langhammer, T. Hellstrom, M. Sandhaug, A. L. Tamber & H. L. Soberg. (2017) Dizziness-related disability following mild–moderate traumatic brain injury. Brain Injury 31:11, pages 1436-1444.
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Mary Miller Phillips & Cara Camiolo Reddy. (2016) Managing Patients with Prolonged Recovery Following Concussion. Physical Medicine and Rehabilitation Clinics of North America 27:2, pages 455-474.
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Donna Ouchterlony, Cheryl Masanic, Alicja Michalak, Jane Topolovec-Vranic & John A. Rutka. (2016) Treating Benign Paroxysmal Positional Vertigo in the Patient With Traumatic Brain Injury. Journal of Neuroscience Nursing 48:2, pages 90-99.
Crossref
Amaal J Starling, Danielle F Leong, Jamie M Bogle & Bert B Vargas. (2016) Variability of the modified Balance Error Scoring System at baseline using objective and subjective balance measures. Concussion 1:1.
Crossref
David X Cifu & Blessen C EapenNeera Kapoor, John-Ross Rizzo, Derrick Allred & Carlos A Jaramillo. 2015. Traumatic Brain Injury Rehabilitation Medicine. Traumatic Brain Injury Rehabilitation Medicine 76 98 .
David J Sharp & Peter O Jenkins. (2015) Concussion is confusing us all. Practical Neurology 15:3, pages 172-186.
Crossref
Heidemarie HallerHolger CramerMarc WernerGustav Dobos. (2015) Treating the Sequelae of Postoperative Meningioma and Traumatic Brain Injury: A Case of Implementation of Craniosacral Therapy in Integrative Inpatient Care. The Journal of Alternative and Complementary Medicine 21:2, pages 110-112.
Crossref
Kathryn J Schneider, Willem H Meeuwisse, Alberto Nettel-Aguirre, Karen Barlow, Lara Boyd, Jian Kang & Carolyn A Emery. (2014) Cervicovestibular rehabilitation in sport-related concussion: a randomised controlled trial. British Journal of Sports Medicine 48:17, pages 1294-1298.
Crossref
Denise R. Kaufman, Mallory J. Puckett, Mitchell J. Smith, Kyle S. Wilson, Rebecca Cheema & Merrill R. Landers. (2014) Test–retest reliability and responsiveness of gaze stability and dynamic visual acuity in high school and college football players. Physical Therapy in Sport 15:3, pages 181-188.
Crossref
Susan B. Perry, Jason Woollard, Susan Little & Kathleen Shroyer. (2014) Relationships Among Measures of Balance, Gait, and Community Integration in People With Brain Injury. Journal of Head Trauma Rehabilitation 29:2, pages 117-124.
Crossref
Bara A. Alsalaheen, Susan L. Whitney, Gregory F. Marchetti, Joseph M. Furman, Anthony P. Kontos, Michael W. Collins & Patrick J. Sparto. (2014) Performance of High School Adolescents on Functional Gait and Balance Measures. Pediatric Physical Therapy 26:2, pages 191-199.
Crossref
Brian J Lithgow & Zahra Moussavi. (2013) A pilot evaluation of vestibular performance using EVestG following mTBI. A pilot evaluation of vestibular performance using EVestG following mTBI.
Ingerid KleffelgaardCecile RoeLeiv SandvikTorgeir HellstromHelene L. Soberg. (2013) Measurement Properties of the High-Level Mobility Assessment Tool for Mild Traumatic Brain Injury. Physical Therapy 93:7, pages 900-910.
Crossref
PATRICIA A. WINKLER. 2013. Neurological Rehabilitation. Neurological Rehabilitation 753 790 .
Brian C. Lau, Anthony P. Kontos, Michael W. Collins, Anne Mucha & Mark R. Lovell. (2011) Which On-field Signs/Symptoms Predict Protracted Recovery From Sport-Related Concussion Among High School Football Players?. The American Journal of Sports Medicine 39:11, pages 2311-2318.
Crossref
Cara Camiolo Reddy. (2011) Postconcussion Syndrome: A Physiatrist's Approach. PM&R 3:10S2.
Crossref
Yuan-Chia Cheng, Wei-Che Lee, Liang-Chi Kuo, Yen-Ko Lin, Chao-Wen Chen, Tsung-Ying Lin & Hsing-Lin Lin. (2011) Use of sodium bicarbonate for acute dizziness after minor head injury. Tzu Chi Medical Journal 23:2, pages 46-50.
Crossref
Velda Bryan. 2011. Vision Rehabilitation. Vision Rehabilitation 301 350 .
Ronald G. RiechersIIII & Robert L. Ruff. (2010) REHABILITATION IN THE PATIENT WITH MILD TRAUMATIC BRAIN INJURY. CONTINUUM: Lifelong Learning in Neurology 16, pages 128-149.
Crossref
Bara A. Alsalaheen, Anne Mucha, Laura O. Morris, Susan L. Whitney, Joseph M. Furman, Cara E. Camiolo-Reddy, Michael W. Collins, Mark R. Lovell & Patrick J. Sparto. (2010) Vestibular Rehabilitation for Dizziness and Balance Disorders After Concussion. Journal of Neurologic Physical Therapy 34:2, pages 87-93.
Crossref
Michelle D. Peterson. (2010) A Case-Oriented Approach Exploring the Relationship Between Visual and Vestibular Disturbances and Problems of Higher-Level Mobility in Persons With Traumatic Brain Injury. Journal of Head Trauma Rehabilitation 25:3, pages 193-205.
Crossref
Karen Bergman & Esther Bay. (2010) Mild Traumatic Brain Injury/Concussion: A Review for ED Nurses. Journal of Emergency Nursing 36:3, pages 221-230.
Crossref
Michael E. Hoffer, Kim R. Gottshall, Ben J. Balough & Bob Moore. 2010. Vertigo and Imbalance: Clinical Neurophysiologyof the Vestibular System. Vertigo and Imbalance: Clinical Neurophysiologyof the Vestibular System 487 490 .
John E. Lopes. (2008) How to evaluate balance disorders in patients in the primary care setting. Journal of the American Academy of Physician Assistants 21:10, pages 38-42.
Crossref
S Perring & T Summers. (2007) Laboratory-free measurement of gait rhythmicity in the assessment of the degree of impairment and the effectiveness of rehabilitation in patients with vertigo resulting from vestibular hypofunction. Physiological Measurement 28:6, pages 697-705.
Crossref

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