This case involves a 41-year-old Caucasian male on active duty in the U. S. Navy. The patient, a Navy Senior Chief Petty Officer Hospital Corpsman, was referred to the NMCSD Physical Therapy Clinic, with vestibular disorder due to a motorcycle accident. The injury occurred on April 30, 2014, when he was hit by a car at an intersection at approximately 35 mph. He had a Glasgow Coma Scale of 15 (mild TBI) on admission to the hospital. Loss of consciousness was for an unknown amount of time but first memory was 4 days after the accident. He sustained a splenic laceration, small intracranial hemorrhage, multiple facial fractures and abrasions. No operative lesions were evident. Splenectomy occurred and the patient was discharged 4 days later.
The patient complained of headaches (rating of 6 out of 10, with 0 representing no pain and 10 representing worst pain possible), insomnia, dizziness with fast movements, and mild cognitive issues (memory and concentration). Headaches were relieved daily with Tylenol. Evaluation by Otolaryngology showed no spontaneous nystagmus, positional nystagmus, or horizontal nystagmus. The sensation of dizziness fatigued with repetition. The patient presented to physical therapy for evaluation 22 days after injury. Initial clinical vestibular assessments were run to measure balance performance and activity. Measures included the Dizziness Handicap Inventory (DHI), a self-report questionnaire that quantifies the impact of dizziness on daily life and is a tool used to help clinicians understand what particular activities are problematic for the patient. The Activities-Specific Balance Confidence Scale (ABC) was also administered to subjectively measure confidence and steadiness while performing specific ambulation tasks (e.g., walk in a crowded mall, get in and out of a car). A computerized dynamic posturography (CDP) (Neurocom Inc, Clackamas, OR, USA) Sensory Organization Test (SOT) was also performed to determine detriments in maintaining postural stability in stance when other sensory cues (i.e., visual, proprioceptive, or vestibular) are unavailable. A Functional Gait Assessment (FGA) was administered to assess ability to perform tasks while walking (e.g., walking with eyes closed, ambulating backward). Computer in-vision tunnel testing of perception time, target following (TF), dynamic visual acuity (DVA), and gaze stabilization (GS) while seated were also performed. These tests assess impairments in a patient's ability to perceive objects accurately while actively moving the head. Lastly, Cervical Joint Position Error Test (Cervical JPET) was performed to assess the cervicocephalic proprioception and neck reposition sense (ability to relocate the head back to center after rotation in transverse and sagittal planes).
Results of these initial tests were as follows:
Dizziness Handicap Inventory: 18 out of 100 (with 0 representing no perceived handicap due to dizziness)
Activities-Specific Balance Confidence Scale: 78 out of 100 (with 100 representing complete balance confidence)
Posturography CDP SOT Score: 60 out of 100 with a reduced vestibular profile (failing score for condition 5: eyes closed on a sway-referenced support)
Functional Gait Assessment: 16 out of 30 (with 30 representing complete ability to perform tasks) - patient considered a fall risk
Cervical JPET deviations:
Right = 4.5'' R, 3.0'' R, 2''R
Left = off R, 6.0'' R, off L
Up = 4.5'' up, 1.0'' L, 2.0'' up
Down = 6.0'' up, 3.0'' up, 2.0'' down
Perception Time: 20 msec
Target Acquisition:
Left: 290 msec
Right: 290 msec
Up: 290 msec
Down: 290 msec
Target Following: 15  per second
Dynamic visual acuity (LogMar) loss:
Right: 0.10
Left: 0.30
Up: 0.10
Down: 0.10
Gaze Stabilization Test: unable to complete.
This patient wanted to remain on active duty and pass the semi-annual Navy Physical Readiness Test (PRT) comprised of sit-ups, push-ups, and a cardiovascular activity (run, swim, bike, or elliptical). In order to do this he needed to increase his running speed to meet the run time standard for 1.5 mile run. The patient scored poorly in walking with vertical head motion, walking with tandem steps, and walking with eyes closed during clinical testing. The short-term goal of walking 20 feet with horizontal head motion without veering side to side was set for 3 weeks into therapy. The long-term goal of being able to perform the DVAT with no more than 0.2 logmar DVA loss was set for 6 weeks into therapy.
After the intake assessments and interview, it was concluded that vestibular rehabilitation would target vestibular ocular reflex (VOR) abnormalities, vestibular spinal reflex (VSR) deficits, and dynamic balance dysfunction. The patient gave written informed consent in accordance with the Institutional Review Board at the NHRC prior to participating in the study.
The treatment plan commenced at the NMCSD vestibular physical therapy clinic with a focus on increasing head movement, balance, and optical stimuli. The basis for the treatment rationale was the standard, documented physical therapy protocol for such an injury and the symptoms presented. The goal was to improve upon balance and ambulation and decrease dizziness, headache, and pain level. Traditionally based vestibular physical therapy was conducted for approximately 2 months, two times per week. Therapy sessions lasted approximately 30-45 min. The retraining exercises help to improve the coordination of body movement and organization of sensory information such as that from vision, balance, and proprioception. Exercises included treadmill walking and standing balance with eyes closed. A home exercise program was also administered involving similar exercises. These involved eye and head movements (both separate, together, and alternating) with a moving printed card; somatosensory exercises with arms crossed, eyes closed and head and weight shifts; and gait in different directions. The patient progressed and was able to stand with eyes closed unassisted, walk outdoors, and perform small bouts of running at slow speeds. However, the patient continued to demonstrate difficulties when walking and turning his head in certain directions and could not run for long periods of time without dizziness.
Since the subject was highly motivated and goals included passing the PRT (requiring running a minimum of 4.9 miles/hr or 2.2 m/s), treatment utilizing treadmill walking and multitasking was implemented. The patient was introduced to therapy techniques utilizing the CAREN (extended, Motekforce Link, Amsterdam, The Netherlands) located at the NHRC in San Diego. The CAREN, an immersive environment with 6 degrees of freedom motion platform and built-in instrumented treadmill, is ideal for assessment and rehabilitation of gait and balance disorders. Patients can interact with the system due to integrated force plates measuring weight shifting and body motion with an embedded motion capture system. Detailed visual displays are projected onto a 180  screen and move in synchronization with platform and subject movements. Immersion is further enhanced with realistic sounds and scents. Numerous biomechanical measurements are recorded, unobtrusively, as patients engage in the CAREN applications. Subjects are secured in a full body safety harness attached to an overhead truss which allows them to move freely on the treadmill. Several applications have been used in conjunction with each other to create a therapy session incorporating physical and cognitive multitasking to simulate real world situations.
Treatment sessions on the CAREN lasted 45 min, once per week for a total of six weeks. The sessions included various immersive applications where the patient had to balance on the moving platform or walk while performing different physical or cognitive tasks (Figure 1). This included the "Endless Road" application where the patient walked on a straight path while performing a series of cognitive tasks, which were presented in order of: (1) direction of optotype letter "E"; (2) addition or subtraction of two numbers; and (3) stroop test (name of a color is displayed on the screen (e.g., "blue," "green," or "red") with uncorrelated font color and the patient either says the word or color of the font). These tasks were given to provide a multitasking component to the activity as well as perform side-to-side head turning (scanning), as the images (numbers and words) were presented randomly on the left and right sides of the screen. The subject chose his own walking speed by pressing buttons to increase or decrease speed using a handheld game controller. After an initial "warm-up" round of the three cognitive tasks, the same tasks were performed again but with the addition of platform motion. This included a platform gyration during the optotype testing, left or right tilt when the math equations were presented, and a left or right shift when the stroop word was presented.
The next application, "Forest Road," consisted of the subject walking on a path with variable terrain. This included walking up and down hills and left and right curves in the path. The platform moved accordingly with the path terrain (platform tilts up and down or platform shifts left and right). At the same time, the subject was given a task of hitting moving objects within the scenery by swatting at them as they passed. An optical motion capture system (Motion Analysis Corp, Santa Rosa, CA, USA) picked up movement of his hands, allowing for interaction with the virtual environment. This multi-tasking application challenged the patient by making him visually follow a moving target while walking over uneven terrain. The patient had to anticipate, plan, and vary his posture and gait in order to successfully hit targets. A scoring system based on walking speed, amount of platform motion, and number of targets hit, engaged the patient and measured his progress over each session.
A third application, "Boat," challenged the patient's balance and visual processing as the subject was tasked to drive a boat through a slalom course using side to side shifting to control the boat's direction left and right and fore-aft movement to control speed. The platform tilted and moved up and down, simulating the boat movement as it went over waves in the water. Platform motion scaling was increased over the visits, as the subject became more comfortable with the scenario. A scoring system based on average speed, number of buoys successfully passed, number of objects hit (counted as a penalty), wave height, and platform scale, allowed the patient to challenge himself and measure his progress over each session.
The fourth application used in the therapy was a "Mountain Patrol" where the subject walked through a simulated mountainous path and patrolled for enemy targets. Motion capture markers placed on an airsoft weapon that the patient carried was used to target and shoot within the virtual scenario. As the patient walked on the treadmill (speed set by the therapist), platform motion mimicked the terrain of the path. The multisensory inputs of moving objects (e.g., Mine-Resistant Ambush Protected (MRAP) vehicle passing by), visual flow, surround sound, platform motion, and targeting while walking made this a challenging task. As this was a longer scenario, the objective was to increase the amount of time that the subject performed the task, up to 10 min in duration, increase walking speed, and vigilance.
The same clinical measurements obtained during the initial assessment (i.e., DHI, FGA, etc.) were also obtained at the 3rd and 6th week of treatment on the CAREN to measure improvements in vestibular function.