AKINETIC
MUTISM
aka Coma
Vigil
Definition:
State of
consciousness with preserved awareness, retention of ability to move and speak
but failure to do so
(immobile and mute but eyes open, follows
environment, but not respond to commands)
- ie. no
deficit in effectors of movement or speech (like a global apraxia of
interaction)
Localization:
1.
Frontal lobe - usually bilateral medial frontal (especially cingulate gyrus)
2. Basal
ganglia - ventral striatum, globus pallidus
3. Fornix
/ limbic system
4.
Thalamus - medial nuclei
5.
Diffuse white matter disease (eg. leukoencephalopathy)
Differential
Diagnosis:
1. Abulia
- milder on spectrum of akinetic mutism, with reduced impulse to act, slow
responses (lack of initiative & spontaneity)
2. Apathy
- dull emotional tone, able to verbalize this lack of interest
- both #1
and #2 are localized to bilateral medial frontal
3.
Depression - flat affect, apathetic (see #2); ? left frontal or anterior
temporal
4. Catatonia
- assoc w/ waxy flexibility, where immobile & mute due to psychiatric
disease
- may
have posturing and stereotypy, even bouts of excitement (can respond to
benzodiazepines)
5.
Extrapyramidal muteness - inability to act due to increased tone and akinesia
(parkinsonism)
- from
basal ganglia disease (incl. neuroleptic malignant syndrome)
6. Locked-in
state: inability to move or talk due to quadriparesis & bulbar
paralysis, only vertical eyes movements and eye blinking may be preserved
(bilateral pontine, eg. basilar occlusion)
7. Persistent
vegetative state: loss of cortical function, no purposeful movements and
unaware of environment but alertness / sleep-wake cycles retained (diffuse
cortical damage)
8.
Aphemia: cortical anarthria but preserved nonverbal / written behaviour (left inferior frontal)
9.
Cerebellar mutism - postoperative syndrome with apathy and mutism +/-
cerebellar dysfunction
Etiologies:
1. Toxic
- Carbon
monoxide intoxication
-
Drug-induced leukoencephalopathies (eg. Methotrexate, 5-FU, Amphotericin)
2.
Infectious / Immunologic
-
Encephalitis (Measles, encephalitis lethargica, arboviruses)
- ADEM or
MS
- HIV
encephalitis
- PML (progressive multifocal
leukoencephaloathy)
3.
Vascular (infarct / hemorrhage)
- ACA
Infarcts esp bilateral (eg. post-SAH): lower limb weakness, sphincter
disturbance
-
Bilateral paramedian thalamic infarcts
- Bilateral
subdural hematomas
-
Vasculitis
4.
Degenerative:
-
Creutzfeld-Jakob Disease
- Frontal-subcortical
dementias (incl. Binswangers)
5.
Neoplastic
-
invading any of above areas (eg. frontal lobes, thalamus)
6.
Traumatic:
- frontal
contusions
7.
Hydrocephalus
8. Drug
toxicity
-
phenytoin, baclofen, disulfiram, cyclosporine (mutism after liver
transplantation)
Work-Up:
Neuroimaging
(preferably MRI)
CSF
analysis (for viral etiologies, 14-3-3 protein?)
Treatment:
Trial of
dopaminergic therapy
-
levodopa/carbidopa or dopamine agonist (eg. bromocriptine)
References:
Cartlidge
N. States related to or confused with
coma. J Neurol Neurosurg Psychiatry
2001; 71 (supp I): i18-i19.
Lim GT,
Mendez MF, et al. Akinetic mutism with
findings of white matter hyperintensity.
J Neuropsychiatry Clin Neurosci 2002; 14: 214-221.
Last
update: August 2003
Reviewed
by: pending review
Neurological
Medicine Pocketbook
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UWO Neurology Residents
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