VESTIBULAR AND

CEREBELLAR ATAXIA

Julius King Kwedhi

ATAXIA DEFINITION The word "ataxia", comes from the

Greek word, "a taxis" meaning "without order or incoordination". The word ataxia means without coordination. (http://www.ataxia.org/learn/ataxia-diagnosis.aspx)

Inability to coordinate voluntary muscle movements; unsteady movements and staggering gait. (WordWeb Dictionary)

NEUROANATOMY OF CEREBELLUM

BLOOD SUPPLY

VENOUS DRAINAGE

THE CEREBELLUM FUNCTION Involved in movement coordination.

Receives sensory information and then influences descending motor pathways to produce fine, smooth, and coordinated motion.

THE CEREBELLUM SUBDIVISIONS

THE ARCHICEREBELLUM (vestibulocerebellum)

Primarily controls posture and balance, also movement of the head and eyes.

It receives afferent signals from the vestibular apparatus and then sends efferent fibers to the appropriate descending motor pathways.

THE PALEOCEREBELLUM (spinocerebellum)

Primarily controls movement of the proximal portions of the limbs.

It receives sensory information on limb position and muscle tone and then modifies and coordinates these movements through efferent pathways to the appropriate descending motor pathways.

THE NEOCEREBELLUM (cerebrocerebellum).

The largest part. Coordinates movement of distal portions of the limbs.

It receives input from the cerebral cortex and thus helps in the planning of motor activity (e.g., seeing an object and then planning and executing the movement of the arm and hand to pick it up).

VESTIBULUM APPARATUS

ELECTRICAL SIGNAL FROM THE COCHLEA

Vibrations of the tympanic membrane Pressure changes imparted on oval window of cochlea Basilar membrane vibration depolarization of hair cells creation of an electrical signal which is transduced through the afferent nerve fibers to cochlea nerve

The cochlea transduces sound into electrical signals.

Axons convey these signals to the dorsal and ventral cochlear nuclei, where it is tonotopically organized.

Following a series of integrated relay pathways, the ascending pathway projects to the thalamus (medial geniculate bodies) and then the acoustic cortex in the transverse gyrus of the temporal lobe, where information is tonotopically represented (low, middle, and high tones).

Three sensory systems serving spatial orientation and posture:

1. The vestibular system2. The visual system (retina to occipital

cortex) and the3. Somatosensory system that conveys

peripheral information from skin, joint, and muscle receptors.

These 3 stabilizing systems overlap enough to compensate (partially or completely) for each other’s deficiencies

SYMPTOMS OF VESTIBULAR ATAXIA Dizziness Vertigo Faintness Disorder of gait (Ataxia, Disorders of

balance) Falls Nausea Vomitting

VERTIGO Physiologic Vertigo

a) When brain is confronted with an intersensory mismatch between the 3 stabilizing sensory systems (e.g. car sickness, height vertigo)

b) Vestibular system is in unusual head movements it’s not adapted to (e.g. seasickness)

c) Unusual head/neck position (e.g. extreme extension when painting ceiling)

d) Following a spin (Physiologic postrotational vertigo) Pathologic Vertigo:

Due to lesions of visual, somatosensory or vestibular systems1) Peripheral vertigo2) Central vertigo3) Psychogenic vertigo

PERIPHERAL VERTIGO Localization of lesions & Common causes: Labyrinthine,• Acute unilateral dysfunction: • Infection, Trauma, Ischemia

• E.g.Occluded labyrinthine branch of auditory artery Labyrinthine Ischemia abrupt onset of severe vertigo, nausea, vomiting

• Acute bilateral dysfunction: toxins, drugs & alcohol• Recurrent unilateral dysfunction: Meniere’s disease• Positional vertigo: Trauma. Aggravated by head

position. Nystagmus – tortional & upbeating. Benign Paroxysmal Position Position(ing) Vertigo BPPV

Vestibular nerve• Diseases affecting the cochlear nerve in petrous bone,

e.g. Tumour (schwanoma). Tinnismus, hearing loss

CENTRAL VERTIGO Localization:• Brain stem & cerebellum

(vestibulocerebellum)

Common causes:StrokeBrain tumorMltiple Sclerosis InfectionBasilar migraine

TREATMENT OF VERTIGO Antimigranous treatment Antihistamines (Meclizine,

Promethazine) Benzodiazepines (Diazepam,

Clonazepam) Phenothiazepines (Prochlorperazine) Anticholinergic (Scopolamine

transdermal) Sympathomimetics (Ephedrine)

CEREBELLAR ATAXIA Mechanism:

Pathology of one or more of the 3 sensory systems serving spatial orientation and posture:1. The vestibular system2. The visual system (retina to occipital

cortex) and the3. Somatosensory system that conveys

peripheral information from skin, joint, and muscle receptors.

FORMS OF ATAXIA Cerebellar Gait Ataxia

A wide base of support, Lateral instability of the trunk, Erratic foot placement, and Decompensation of balance when attempting

to walk tandem. Early feature: Difficulty maintaining balance

when turning. Patient unable to walk tandem heel to toe, and

display truncal sway in narrow-based or tandem stance.

Patient show considerable change in their tendency to fall in daily life.

CAUSES OF CEREBELLAR GAIT ATAXIA Alcohol Hereditary cerebellar degeneration (e.g.

multiple system atrophy) Stroke (in elderly) Trauma Tumour Neurodegenerative disease (e.g.

multiple system atrophy)

SENSORY ATAXIA Balance depends on:

high-quality sensory information from the visual system the vestibular systems and proprioception.

Balance impairment and instability due to loss or degradation of sensory information, leading to:Sensory ataxia of tabetic neurosyphilis,

CAUSE OF SENSORY ATAXIA

Neuropathy affecting large fibers. Vitamin B12 deficiency

(demyelination large-fiber sensory loss in the spinal cord and peripheral nervous system)

SYMPTOMS OF SENSORY ATAXIA Diminished joint position and vibration

sense in the lower limbs. Destabilized standing posture with eyes

closed Patients often look down at their feet

when walking and do poorly in the dark. Imbalance due to bilateral vestibular loss,

caused by disease or by exposure to ototoxic drugs.

REFERENCE Rohkamm R,. (2004). Colour Atlas of

Neurology, Thieme, Stuttgart, Germany Netter F. H., et al (2004). Atlas of

Neuroanatomy And Neurophysiology, Stalevo, USA

Hauser S. L.,& Josephson S. A., (2010). Harrison’s Neurology In Clinical Medicine, McGraw Hill Medical, New York, USA