Why am I dizzy? Flashcards
What are the components needed to achieve good coordination and balance?
- Know where the head is.
- Know where the limbs are.
- Be able to detect position of body parts.
- Be able to detect motion - in all planes, acceleration and deceleration.
- Integrate with vision.
- Central control systems - voluntary and involuntary.
- Integrate motor control and output.
What is the commonest cause of vertigo?
BPPV (benign paroxysmal positional vertigo)
What is BPPV?
- Benign paroxysmal positional vertigo - due to an inner ear problem.
- Vertigo is an abnormal sensation of movement.
What are the different parts of the body which can be affected by dizziness?
The vestibule has 2 otolith containing organs.
What are they?
What is their function?
- Saccule macula (continuous with cochlea).
- Utricle macula (continuous with semi-circular canals).
- Monitor position of head relative to force of gravity.
- Saccule - monitors vertical movements (s for sky!).
- Utricle - monitors horizontal movement.
What is static tilt and linear translation?
- Hair cells, project hairs into an otolithic (ear stone) containing gelatinous structure.
- Cilia + kinocilium - provide directional information.
- Movement of otolithic membrane (from tilting or translational movement) bends the cilia / kinocilium in a very direction specific way.
- A 0.5 micron of the kinocilium opens / closes the hair cell cation channels.
How is static tilt and linear translation translated to head position?
How is rotational acceleration detected?
- Rotational acceleration is detected by the semicircular canals.
- Monitors rotational acceleration and deceleration.
- Three planes of orientation.
- Within each canal is semi-circular duct.
- Within duct, ampulla.
- In the ampulla there are supporting cells, hair cells, cilia and kinocilium.
What are the directions of rotation?
- Roll
- Pitch
- Yaw
How is dynamic equilibrium detected?
- Measures the changes in rotation.
- Signal transduction (as before).
- Resting rate of transmitter release.
- Bending in one direction (towards the kinocilium) results in depolarisation and increased action potential rate.
- One side of the head depolarises; the other hyperpolarises.
Describe the test used to detect a particle in the semicicrular canals.
- Upbeat nystagmus to the side of the lesion upon lying the patient down with head over the end of the bed.
Describe the epley manoeuvre.
https://www.youtube.com/watch?v=kEM9p4EX1jk
What is Ménière’s disease?
- The vestibular apparatus is bathed in endolymph.
- Normally drains to venous sinus.
- Build-up can cause Ménière’s disease (vertigo, nausea, tinnitus and hearing loss).
Describe the caloric test.
- A test for the condition of the brainstem.
- Putting warm water in the external meatus of a patient sets up calorically induced movements in the labyrinth system.
- Nystagmus pattern for a movement towards the irrigated ear with warm water is slow away from direction of rotation and a fast return in the same direction of rotation.
- Cold water does the opposite (COWS - cold opposite, warm same - refers to fast component).
- In comatose patients there is no fast saccade, only the slow component.
- Brain stem death, no vestibulo-ocular reflexes. I.e. if there is no nystagmus upon the injection of hot or cold water, the patient is brainstem dead.
Summarise the systems for movement.
Describe how the components of the cerebellum function in coordination of motor output.
Identify the structures.
Identify the features of the flattened cerebellum.
Identify each feature of the cortical cerebellar structure.
What are the principal afferents of the cerebellum?
Describe the cerebellar output.
- All via deep nuclei.
- From lateral to medial:
- Dentate nucleus
- Emboliform nucleus
- Globose nucleus
- Fastigial nucleus
