Acquired Brain Injury

Acquired brain injury

any sudden, non-progressive or non-degenerative change in neurological processing due to internal (non-traumatic infection, stroke, vestibular dysfunction, tumor, etc.) or external (traumatic) causes. Does not include congenital or degenerative disorders and birth trauma.

Traumatic brain injury

disruption of normal brain function caused by head injury (blow, jolt, penetration, etc). Is classified base on severity as it can present with a wide range of dysfunction. Is the leading cause of neurologic disability in the US.

Fall

the leading cause of TBI

30.5%

percentage of injury related deaths in the US attributed to traumatic brain injury

Glasgow Coma Scale

scale (3 to 15) used to classify the severity of traumatic brain injury based on ocular, verbal, and motor responses.

Diffuse axonal injury

the most common pathological feature of traumatic brain injury occurring due to mechanical forces and secondary strain and shearing of axons. Results in a buildup of transport product and the release of free radicals. Is delayed occurring hours to weeks post injury. Neuroimaging appears normal due to diffuse damage that cannot be detected.

Coup

injury to the brain at the point of contact

Contre-coup

injury to the brain opposite to the point of contact

Chronic traumatic encephalopathy (CTE)

delayed progressive, degenerative disease of the brain found in those with a history of repeated brain trauma or concussive events. Degeneration occurs due to a buildup of tau protein. Results in memory loss, confusion, impulse control problems, aggression, and depression. Can only be diagnosed post-mortem.

80%

percentage of patients with traumatic brain injury that complain of dizziness and balance problems likely secondary to vestibular deficits.

Disequilibrium

sensation of walking on uneven ground

Dizzines

subjective feeling of nausea, light-headedness, or disorientation

Visual motion sensitivity

dizziness that is provoked by full field repetitive or moving visual environments

Vertigo

illusion of movement of surroundings

Vestibular

Proprioception

Visual

3 Afferent Systems Controlling Balance

Musculo-skeletal

Oculomotor

2 Efferent Systems Controlling Balance

Vestibular nuclei

Cerebellum

Cerebrum

Superior colliculus

4 Integrative Systems Controlling Balance

-Otologic (inner ear infection)

-Unknown (brain filtering problems)

-Psychological (anxiety)

-Central/neurologic (stroke, head trauma)

-Medical (low blood pressure)

5 Causes of Dizziness (most to least common)

Anticonvulsants

Antihypertensives

Ototoxic drugs

Psychotropic agents

Stress reduction drugs

5 Medications Causing Dizziness

mycin antibiotics, anti-cholinergic

two ototoxic drugs causing dizziness

Vestibulo-ocular reflex

reflexive gaze stabilization that functions to maintain a steady image on the retina during head movement. Requires communication between the vestibular and visual systems.

3, 6, 8, MLF

In the vestibulo-ocular reflex CN _____ (2) communicate with CN ____ via the _____ to generate horizontal eye movements in response to head movement

Anisometropia

Uncorrected astigmatism or HA

Multifocal lenses

Glare

4 Optical Causes of Vestibular Problems

50%

percentage of cranial nerves that impact visual function directly or indirectly. Neurons involved in visual function travel to all four lobes of the brain, not just the occipital lobe

2, 3, 4, 6

four cranial nerves impacting visual function directly

5, 7, 8

three cranial nerves impacting visual function indirectly

Ventral stream (what)

pathway connecting the occipital lobe to the temporal lobe playing a role in object recognition, memory, and emotion. Is less commonly affected in traumatic brain injury.

Dorsal stream (where)

pathway connecting the occipital lobe to the parietal lobe playing a role in spatial orientation and multisensory integration. Is more commonly affected in traumatic brain injury.

Prefrontal

portion of the parietal lobe that functions in the control of eye movements and spatial working memory (visuospatial processing)

Premotor

portion of the parietal lobe that is responsible for mapping of objects in space and coordination body position (visually guided actions)

Medial temporal

portion of the parietal lobe that updates body position during navigation

vergence

pursuits

saccades

fixation

accommodation

Dorsal ventral stream miscommunication results in a difficulty to locate objects in space impeding on visual functions such as... (5)

-Address optical and visual input problems

-Address non-optical visual triggers

-Strengthen the connection between eyes and brain

3 Roles of Optometry in Vision Rehabilitation

Accommodative insufficiency

most common accommodative defect diagnosed following acquired brain injury

Saccade deficit

most common versional defect diagnosed following acquired brain injury

CN palsies 3, 4, 6

INO

Skew deviation

Consider these 3 conditions in vergence defects following acquired brain injury...

Convergence insufficiency

most common vergence defect diagnosed following acquired brain injury

Scattered, non-lateralized

visual field defect that is more commonly associated with diffuse damage caused by traumatic brain injury rather than stroke.

Lateralized

visual field defect that is more common in stroke rather than traumatic brain injury.

right brain lesions

Inattention of a visual field defect is common with...

-Illness (I.e. barometric pressure changes in those with vestibular dysfunction)

-Fatigue

-Controlled substances

-Changes in stress

4 Factors Exacerbating Symptoms

-Exam not exceeding 1 hour

-Dim lighting

-Speak clearly and slowly

-Slow changes in prism magnitudes

-Have patient close eyes between tests

Clinical Pearls for examining traumatic brain injury

Nature/date of the insult

History of hospitalization

Loss of consciousness

Therapies received

History of Acquired Brain Injury (4 important aspects)

nystagmus

During visual acuity testing in patients having acquired brain injury it is important to note any ____ eye movements

Lid asymmetries

Pupil dysfunctions

Facial asymmetries

External Examination of TBI cases be keen to notice... (3)

Over/under shooting

Unsteadiness

Slow reaction time

Head/body movement

Observation of Saccades in TBI (4)

15-0.25(age) - formula for expected minimum accommodative amplitude

+0.50-0.75

expected FCC/MEM results

+2.00/-2.37

expected NRA PRA results

8 cpm

expected BAF results

11 cpm

expected MAF results

4:1

expected ACA ratio

15 cpm

expected vergence facility results

5/7 cm

expected NPC results without RG glasses

7/10 cm

expected NPC results with RG glasses

Tannen Prism Flipper Test

Name this test: 2 BI/4 BO prism flipper is utilized 15 feet from a 20/30 letter. Is used to evaluate distance fusional facility in TBI

concussion, visual motion sensitivity

Distance fusional facility may be reduced in patients having ____ suggesting ____

15 cpm

normal tannen prism flipper test results

10 cpm

tannen prism flipper test results that will make the patient visually symptomatic

2 lines

Patient must have their visual acuity tested with head movement (dynamic VA). If there is a drop in acuity of ____, this is pathognomonic for a visual vestibular issue

VOR

Dynamic visual acuity assesses _____ response

sensitivity to movement in the peripheral field

peripheral OKN can be performed to Assess...

Abnormal egocentric localization (Visual midline shift syndrome)

patient's perception of their body position is different from what is actually occurring. Commonly occurs with hemiparesis or hemiplegia. Patient will lean away from the paretic side and will have an abnormal gait.

Yoked prism

prism equal in magnitude and direction which can be useful in the treatment of abnormal egocentric localization.

Visual neglect (visual spatial inattention)

condition where the region of space contralateral to the brain lesion is perceived as not existing (I.e. denying of the existence of contralateral limb)

Right

____ sided spatial neglect is rare due to the redundancy of the visual system where this field is controlled by both the right and left sides of the brain

Divergence excess

vergence disorder that is rare in acquired brain injury and likely represents a long standing binocular dysfunction

50

Photophobia is reported in ____% of patients following traumatic brain injury

balance stability

An omega blue tint is useful for the "dizzy" patient as it provides...

general photophobia

A grey or brown tint is useful for...

migraine

The FL 41 tint is useful for...

before

Underlying binocular vision dysfunctions must be addressed ____ initiating visual field expansion procedures

10-15 PD

amount of yoked prism used for stationary viewing

6-10 PD

amount of yoked prism used for reading

Peli Prism (40 PD BO)

what is this visual field expansion technique?

Hemi Field Prism (18-20 PD)

what is this visual field expansion technique?

Bottom up processing

reactive processing that depends on the brain's reception of stimulus. Is mediated by sensory cues of blur and retinal disparity. I.e.) stubbing your toe on a chair

Top down processing

voluntary processing that involves cognitive control and selective attention. I.e.) avoiding a chair that you previously stubbed your toe on

Fronto-parietal

regions of the brain responsible for top down processing