Cerebellar Disorders

Basics of the Cerebellum

Landmarks – organized in a vertical fashion

midline of cerebellum (vermis) represents midline of body (equilibrium mvmnts – posture; eye movements – saccades)

right side for right limb movements and left side for left limb movements (stance, head and eye movements)

superior- inferior – body represented upside down Þ top is legs and bottom is head

The cerebellum is involved in control of: coordination of skilled movement, equilibrium, posture, muscle tone

Cerebellar Lesions – the main clinical effect of a cerebellar lesion is a type of incoordination known as ataxia

ATAXIA – Abnormalities in the rate (slow and erratic timing), range (dysmetria, an inaccuracy that may result in overshooting or undershooting targets) and force of movement

Other clinical effects of cerebellar lesions include:

speech: dysarthria (problem of articulation – slurred), "scanning" cadence (pause between syllables), explosive speech (lack of control over the force of air expulsion)

ocular movement: nystagmus (drifting of the eyes off target) dysmetric saccades – undershoot target or overshoot target then eyes have to come back to focus on the target

gait: disequilibrium or impairment of balance, wide-based gait, tendency to stagger or veer off course (walk like a drunk)

tremor – see below

Tremor

Definition: continuous, rhythmic oscillation of a body part; continuous (uninterrupted), rhythmic (regular, periodic), oscillation (equal to and fro)

Classifiction: relationship to activity, distribution (proximal vs distal limbs affected), frequency (how often a tremor occurs in a given period of time)

Cerebellar tremors: distribution (proximal muscles of limbs, head ("titubation" – where head bobs back and forth in a rhythmic fashion), frequency = 2-3 Hz (very slow)

Cerebellar tremors: ataxic tremor (horizontal sway occurs with movement, worse nearing a specific target), rubral tremor (at rest, worse with posture, worst nearing target), wing-beating tremor (flapping or arms in "winged" posture)

Other tremors

Enhanced physiologic tremor: occurs with sustained posture and movement; affects all limbs, whole body when standing; frequency (8-12 Hz (very fast)); irregular amplitude

seen with stress, fatigue, anxiety, alcohol withdrawal; can be metabolic cause: hyperthyroidism, hypoglycemia, fever
drugs can be a cause: theophyllines, adrenergics, lithium, antidepressants, caffeine, amphetamines, many others

Resting tremor: occurs when muscles are inactive

distribution: all limbs, lower part of face

frequency: 3-6 Hz (slow)
caused by Parkinson’s disease, dopamine receptor blockers

Action tremor (essential): occurs with sustained posture ("postural") or during movement ("kinetic")

distribution: upper limbs, head, voice

frequency: 6-11 Hz (fast)

Parkinson’s Disease

Clinical Features: tremor, rigidity, akinesia, postural disturbances ("stut" posture – flexion of knees and other joints; patients look older than they actually are)

akinesia: lack of movement

bradykinesia (speed): slow initiation and execution

hypokinesia (size): short stride, micrographia

oligokinesia (quantity): facial expression, staring with little blinking, arm swing); tendency to fatigue with repetition

testing for it: give a task of repetition (write a sentence 3 times) – sentence becomes squiggly and unreadable due to loss of stamina (micrograpnia – smallness of handwriting)

where is site of lesion? 1817 shaking palsy – due to nerve cells in substantia nigra (loss of pigment in the area of the substantia nigra) – nerve cells are responsible for dark pigment and in Parkinson’s most of the nerve cells are gone

pathologic hallmark is cell with "Lewy" body inclusion

substantia nigra secretes dopamine that has negative effect on acetylcholine

during parkinson’s disease Þ too much acetylcholine

treatment: increase dopamine or decrease acetylcholine

Parkinson’s disease vs. essential tremor – similar symptoms, totally different treatments

	Parkinson’s	Essential tremor (action tremor)
relation of tremor to activity:	rest> action	postural-action
distribution	arms, legs, lower face	hands, head, voice
family history	unusual	common
age of onset	50-70	any, most > 50
initial history	week-months	months-years

Treatment for Parkinson’s: levodopa, bromocriptine, pergolide, anticholinergics, amantadine, selegiline

Treatment for essential tremor: propranolol (beta blockers), primidone, benzodiazepines