Neuroanatomy 16: Basal Ganglia
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Movement Disorders = abnormal movements resulting
from basal ganglia pathology; also referred to as
extrapyramidal syndromes
o Other system lesions -> spasticity (UMN lesion;
slow stiff movement with hyperreflexia), ataxia
(cerebellar lesion; irregular uncoordinated
movement) or dyskinesia (basal ganglia
dysfunction; abnormal movement)
o Sometimes abnormal movements from psych
disorders (i.e. conversion disorder)
Basal ganglia are part of loop with major influence on
descending motor systems (via motor and premotor cortex)
Unilateral movement disorders caused by focal basal ganglia lesions (infarct, hemorrhage,
abscess, tumor or degeneration) -> movement disorder is contralateral to lesion
During sleep, palatal myoclonus, periodic leg movements, and some tic disorders still occur but
movement disorders may cause insomnia.
Bradykinesia = slowed movements; hypokinesia = decreased movement; akinesia = absence of
movement
o Lesion not in levels higher than upper motor neurons; only by increased inhibitory basal
ganglia outflow to thalamus (via internal globus pallidus and substantia nigra pars
reticulata)
 Ex. loss of dopaminergic nigrostriatal system, loss of inhibitory path from
striatum to substantia nigra and internal pallidum or loss of inhibitory neurons
from external pallidum to subthalamic nucleus
o Diffuse frontal lobe, subcortical white matter, thalami or brainstem reticular formation
lesions – decreased spontaneous movement (abulia and akinetic mutism)
o Depression and advanced schizophrenia cause psychomotor retardation = catatonia
Rigidity = resistance to passive movement of a limb
o Clasp-knife rigidity = increased as muscles stretched and then decreased (corticospinal
disorder)
o Plastic, waxy or lead pipe rigidity = continuous rigidity (basal ganglia disorder)
 Cogwheel rigidity = seen in parkinsonian disorders; ratchet-like interruptions as
limb is bent (rigidity with superimposed tremor)
o Paratonia or gegenhalten = actively resist movement (frontal lobe dysfunction)
Dystonia = distorted positions
o Focal dystonias = torticollis, blepharospasm (facial muscles around eye), spasmodic
dysphonia (laryngeal muscles), writer’s cramp -> basal ganglia dysfunction
o Respond well to botulinum toxin (blocks Ach release)
o Primary idiopathic torsion dystonia = generalized hereditary disorder
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Seen in tumor, abscess, infarct, CO poisoning, Wilson’s, Huntington’s and Parkinson’s
diseases, focal seizures, long term use of antipsychotic and anti-emetic medications
(produce tardive dyskinesia which persists after stopping)
Wilson’s Disease = autosomal recessive disorder of biliary copper excretion (liver and basal
ganglia degeneration) -> dysarthria, dystonia, rigidity, tremor, choreoathetosis, “wing beating”
tremor, risus sardonicus (wry smile)
o Kayser-Fleischer rings in cornea, high urine copper, ceruloplasmin low
o Treat with penicillamine or zinc (test siblings)
Athetosis = writhing, twisting movement; may merge with choreic movements ->
choreoathetosis
o Causes: preinatal hypoxia, kernicterus, Wilson’s disease, ataxia telangiectasia,
Huntington’s disease, medications, Parkinson’s disease with levodopa
Chorea = continuous involuntary fluid or jerky movements (may be confused as restlessness)
o Resembles frantic break dancing
o Cause: Huntington’s disease (also have neuropsych disturbance), benign familial chorea
(autosomal dominant inheritance), perinatal anoxia, CO poisoning, hyperthyroidism,
hypoparathyroidism, Lesch-Nyhan syndrome, side effect of levodopa, antipsychotic or
anti-emetic medications
o Sydenham’s (rheumatic) chorea (where group A strep infections untreated) ->
adolescence, females, impulsive behaviors, antistrep antibodies cross react with striatal
neurons
o Systemic lupus erythematosus (SLE) = antinuclear antibody or rheumatological blood
test positive
o Chorea gravidarum = during pregnancy or with oral contraceptives (initial episode of
SLE or Sydenham’s chorea)
o Hemichorea = contralateral to lesion of basal ganglia
Ballismus = proximal limb muscles, large amplitude
o Hemiballismus = most common type contralateral to lesion
o Cause: lacunar infarct of subthalamic nucleus, unilateral basal ganglia lesions
(hemorrhage, tumor, infection, inflammation)
o May progress to choreothetotic movement and treated with dopaminergic antagonists
(haloperidol)
Tic = motor action with urge to perform and relief after
o Motor tic = face or neck
o Vocal tic = grunts, cough, sounds, howling or barking or obscene words (coprolalia)
o Tourette’s syndrome = [persistent motor and vocal tics, boys, autosomal dominant;
increased incidence of ADHD and OCD
 Important to counsel and educate patient, family and other contacts
 Haloperidol or pimozide (dopaminergic antagonists ) beneficial; clonidine
(alpha2 receptor antagonist) being tried
Myoclonus = fastest of all movement disorders
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Causes: anoxic brain injury, encephalitis, toxic/metabolic encephaolpathies, epilepsy,
paraneoplastic disorder (small cell lung, ovarian or breast carcinoma, neuroblastoma),
cortical basal ganglionic degeneration, Creutzfeldt-Jakob disease, lysosomal storage
disorders, late Lewy body disease or Alzheimer’s.
o Asterixis or flapping tremor = in toxic or metabolic encephalopathies (hepatic failure ->
liver flap) -> hold hands in “stop traffic” position.
 Interruptions in contraction of wrist extensors = negative myoclonus
Tremor = oscillating movements, both agonist and antagonist muscles activated (slow or fast)
o Resting tremor (aka Parkinsonian or pillrolling) = asymmetrical, hands and upper
extremity usually, 3-5 Hertz
o Postural tremor = when limbs actively held
 Essential tremor = most common of
all movement disorders, 5-8 Hertz,
hands and arms bilaterally usually,
difficulty holding glass of water or
handwriting; increases with stress,
better with B-andrenergic
antagonists (propranolol) or
primidone, sever cases use
ventrolateral thalmotomy or
thalamic stimulation
 Causes: drugs, metabolic
derangement, withdrawal, fear,
anxiety, enhancement of
physiological tremor
o Intention (ataxic or kinetic) tremor =
feature of appendicular ataxia, 2-4 Hertz
o Action tremor -> postural or intention tremor or both
o Static tremor -> resting or postural tremor
o Terminal tremor -> toward end of movement, postural tremor at final position
o Rubral tremor -> lesion of superior cerebellar peduncle, 2-4 hertz, low amplitude but
violent with movement (with multiple sclerosis or brainstem infarct)
o Palatal tremor/myoclonus -> persistence during sleep, biphasic movement, 1-2 hertz,
lesions of central tegmental tract (brainstem infarct or MS)
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Huntington’s Disease: autosomal dominant with complete penetrance, choreiform movement
disorder, dementia, and psychiatric disturbances, onset 30-50 y.o.
o Progressive atrophy of the striatum (especially caudate nucleus)
 Initially affects striatal neurons of indirect pathway (larger lateral ventricles on
MRI)
o Abnormal body movements, eye movements, emotions and cognition
 Slow saccades, impaired smooth pursuit, sluggish optokinetic nystagmus,
difficulty initiating saccades
o Depression, anxiety, OCD, destructive manic-like behavior, psychosis, memory disorder
(recent and remote), anomic aphasia, impaired executive functions
o Advanced: demented and lose of all purposeful movement, bed-bound, can’t speak, die
of respiratory infections (15 year survival)
o Gene: on chromosome 4 with CAG repeats (normally <34 CAG; Huntington’s > 40 CAG)
 Higher #CAG repeats, earlier onset
o Treatment relieves symptoms only -> use tetrabenazine (depletes dopamine) or block
dopa receptor
Stereotactic surgery = precise 3D localization of brain; apply reference points to skull and obtain
CT or MRI -> use to guide needle or probe through small hole in skull (local anesthesia) giving
permanent lesion
o Used to obtain a biopsy, drain abscesses, during radiation therapy (stereotactic
radiosurgery) to target specific location
Neurostimulation = electrical stimulation of peripheral nerves, SC, cerebral cortex, deep brain
o Can treat pain, movement disorders, epilepsy and psych diseases
o Deep brain stimulation (DBS) = in basal ganglia or thalamus, used over stereotactic
surgery, reversible and flexible adjustment; involves depolarization block by implanted
stim device externally programmed
Lesioning procedures: pallidotomy (internal globus pallidus), thalamotomy (VLp nucleus of
thalamus), subthalamotomy (subthalamic nucleus)
o Treat refractory Parkinson’s disease, dystonia, and essential tremor
 In advanced Parkinson’s or refractory dystonia, target subthalamic nucleus or
internal globus pallidus (contralateral to side of worse deficits)
 Essential tremor associated with discharge in VLp or ventral intermediate
nucleus (VIM) = main thalamic relay for cerebellar output
o Improve drug induced dyskinesias
Transplantation of fetal midbrain neurons or adrenal chromaffin cells in striatum for Parkinson’s
disease treatment also tried
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Parkinson’s Disease: loss of dopaminergic neruons in substantia nigra pars compacta,
asymmetrical resting tremor, bradykinesia, cogwheel rigidity, and postural instability
(parkinsonian gait)
o Parkinsonism and parkinsonian signs have features od the disease
o Idiopathic, onset 40-70 y.o., pale substantia nigra, remaining neurons have Lewy bodies
(eosinophilic, ubiquitin and α-synuclein with halo), initially unilateral and progresses to
bilateral (asymmetrical)
o Diagnosed based on clinical features and improves when treated with levodopa
 Progression is usually insidious (5-15 years)
 Carbidopa (or outside of US use benserazide) -> peripheral dopa decarboxylase
inhibitor used concurrently
 Side effects of peripheral dopamine = GI disturbance, orthostatic
hypertension
 Wearing off of treatment can lead to freezing of pt or may develop dyskinesia
from treatment
 COMT and MAO inhibitors, anticholinergic agents (benztropine mesylate
[Cogentin] and trihexyphenidyl [Artane]), antiviral agent (amantadine),
ropinirole and pramipexole (dopamine agonistst), selegine (inhibits dopa
breakdown), rasagiline (MAO-B inhibitor) may be used in treatment
o Masked facies or hypomimia = decrease in blink rate and facial expression
o Voice becomes hypophonic, slow saccades, micrographia (small writing), retropulsion
(several backward steps to regain balance), use hands to rise from chair, hard to initiate
gait (festinating gait with anteropulsion), en bloc turning, Myerson’s sign (can’t
suppress blink when glabella is tapped), anosmia (impaired smell early in course)
o Advanced Parkinson’s -> dementia (15-40%), bradyphrenia (response to questions
slow), depression and anxiety, seborrhea and hypersalivation, on-off phenomena
(dyskinesia and immobility)
Dopaminergic antagonists (haloperidol [Haldol] and prochlorperazine [Compazine]) cause
parkinsonian signs rigidity, hypokinesia, resting tremor with abrupt symmetrical onset
Parkinsonism plus syndromes = symmetrical symptoms, no resting tremor, early postural
instability (atypical parkinsonism)
o Multisystem atrophy -> striatonigral degeneration, Shy-Drager syndrome,
olivopontocerebellar atrophy
 Insensitive to levodopa due to loss of striatal neurons to globus pallidus and
substantia nigra pars reticulata
o See Table 16.5