Behavioral Neurology
Behavioral Neurology
(Cognitive and Behavioral Neurology)
- is dealing with disorders of higher nervous functions
resulting from structural brain damage (directed attention,
mood, gnostic functions, cognitive functions, memory, …)
- investigates a relationship between brain and behavior,
between brain and mind
- relatively young, interdisciplinary field of study – neurology,
psychiatry, neuropsychology
- in the past BN dealt mainly with dementias and aphasias,
currently BN is rather focused on frontal and temporal lobe
syndromes, consciousness (awareness) and attention,
agnosias, and many other aspects of HNF.
Phineas Gage
• 1848, New England
• PG, 25 years, efficient and faithful foreman on the railroad
construction through Vermont.
• When preparing the rock shooting PG mistakenly ram down
powder and detonator with iron rod (needful sand was
missing).
• During the explosion the iron rod (length 1 m, diameter 4 cm,
6 kg) threw open Gage’s left cheek, bashed in the base skull,
passed over the ventral part of the brain and catapulted
through crown of the head.
• Personality change: „he started to be volatile, impolite, time
to time he was extremely foul-mouthed and stubborn“. For
incredibility he lost a good job, rotated with many work places
(incl. career in circus), he became an alcoholic and
desperate. The neurological status was otherwise normal.
• He died in 38 years because of status epilepticus.
H. Damasio, 1992
Patient H.M.
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Intractable temporal lobe epilepsy from the age of 16 yrs
1953 – W. Scoville – bilateral resection of mesiotemporal regions.
Postoperatively persisted serious anterograde amnesia (impairment of
storage)
Examination of mental functions
• It should be a requisite part of standard neurologic
examination – at least Mini Mental State Examination
should be performed in neurologic pts.
• It has to be systematic and hierarchic
(level of consciousness  directed attention  cognition, mood,
speech)
• Golden neurologic rule „to localize a lesion“ should
be applied for mental functions too (neuronal networks).
• Extremely important is thorough history taking (changes
in pt’s behavior) and focusing on the pt’s behavior during
the examination (evaluation of his/her appearance, cooperation,
attention, memory, mental flexibility, social adaptability, ability of
nonverbal communication, depressive symptomatology, etc.).
Bedside tests of attention
• Luria (fist-palm-side) test
• Luria sketch (visual completion test) (alternating square and pointed figs.)
• Continuous performance test
After registering target digit in presented digit chain a subject has to knock on a table
4-9-1-7-5-4-0-7-9-2-4-3-7-5-0-2
• Digit span test (3-7) – subject has to learn and repeat long digit
chains, also test on short-term memory
Large-scale neural network for directed attention
(Mesulam MM)
Neglect syndrome
= a failure to report, respond, or orient to contralateral novel
stimuli that is caused by damage of large-scale neural
network for directed attention and not by an elemental
sensorimotor deficit.
It is a form of selective unawareness.
Pts with neglect syndrome often appears to be unaware of
contralateral stimuli, they ignore these items, and do not
react to them.
Within neglect there can be hemiakinesia (motor neglect =
movement deficiency = pseudohemiparesis), anosognosia
and/or anosodiaforia (absence of concomitant emotions for
serious functional deficit).
Bedside memory testing is limited
episodic m.
(autobiographic data)
(mesiotemporal regions
– hipp,entorh, perirh, GP)
long-term m. (> 1 min)
Explicite memory
(declarative)
semantic m.
(encyclopedic knowledge)
(more extensive reg. – MT+LT,P,O)
F
(visual x verbal, recall
x recognition)
short-term (working) m. (30-40 s)
(digit span)
(DLPFC + associative visual and auditory areas)
procedural m. (completing word fragment, m. for movements)
Implicit memory
(subcortical circuits – BG, cerebellum + ctx visual, motor,..)
demonstrated by completion
priming
of tasks that do not require
conscious processing
= the ability to acquire a motor skills or cognitive routines by experience
HOSP----
Disorders of symbolic functions
Dysphasia - disorders of speech (Motor or expressive /Broca΄s/
dysphasia; Sensory or receptive /Wernicke΄s/ dysphasia; Global
dysphasia). DOMINANT HEMISPHERE
Aprosodia – impairment of affective component of speech (speech
melody, intonation, voice timbre, use of pauses, etc.) řečově
nedominantní hemisféra). NON-DOMINANT HEMISPHERE
Dressing apraxia - difficulties in dressing, e.g. Getting arm into
pyjamas, …
Constructional apraxia – innability to copy geometrical pattern
Alexia - disturbance of reading (angular or lingual g. within dominant
hemisphere).
Agraphia - disturbance of writing (GFM or PO junction of the
dominant hemisphere).
Acalculia - disturbance of calculation (dominant hemisphere, also
within the Gerstmann΄s syndrome – angular g.).
Gnosis – greek „cognition“
• Gnostic function = an ability to know (recognize) individual objects
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AGNOSIA (without recognition) – def. = impaired recognition of an object which is
sensorially presented while at the same time the impairment cannot be reduced
to sensory defects (intact primary sensory cortex), mental deterioration, disorders
of consciousness and attention, or to a non-familiarity with the object.
The term agnosia is from S. Freud (1891)
Finkelnburg 1870 – „asymbolia“
Jackson 1876 – „imperception“
Munk 1881 – „seelenblindheit“(mind blindness) /X cortical blindness/
Affected individuals behave as seeing (…) the object for the first time in their life.
Beware of erroneous diagnosis of agnosias!
- darkness or very rapid object presentation
- unfamiliar objects (e.g. tuning fork)
- insufficient instructions
- overlooking another disease (polyneuropathy, cataract,
otosclerosis,…)
- aphasic phenomena
- apraxic phenomena
Agnosias are related to the lesions within associative cortices and their
very surrounding but also with disconnections (impairment of the
corpus callosum or long fibers within the white matter).
Unfortunately in the practice agnosias are often associated with other
neurologic deficits (aphasia, apraxia, behavioral disorder)! Resulting
clinical manifestation is therefore highly individual.
Visual agnosia
Specific impairment of recognition of visually presented objects – pt is well seeing but he/she is
not able to identify these items.
Clinical classification according to the character of impairment:
Apperceptive visual agnosia – patient is neither able to recognize objects
visually nor their form, and is not able to describe it correctly.
Associative visual agnosia – patient is not able to recognize objects but
he/she can describe the form or even is able to draw the object correctly.
According to the type of affected stimuli:
- Agnosia for objects
- Agnosia for colors
- Akinetopsia
- Prosopagnosia
- Simultanagnosia
- Pure alexia
- …..
- Agnosia for objects (by definition pts are not able to recognize objects when they
are solely presented visually. Usually visual object agnosia was considered as the
classical example of agnosias, but frankly it is very rare type of visual agnosia. The
most frequently it arises from bilateral (rarely just left-sided) damage of lateral parts
of occipital lobes (strokes).
- Agnosia for colors (coloragnosia) – the loss of ability to recognize colors as an
acquired disorder. Pt is unable to recognize colors, but he/she understands colors
and is able to correctly name e.g. the color of banana, orange, etc. (lesion within left
occipital lobe – prestriatal cortex – ventral visual stream). It needs to be
differentiated from from inability to name colors!
- Hemiagnosia for colors – the inability to recognize colors confined to one half of
the visual field – maybe attention defect (similarly to “unilateral spatial agnosia“)?
- Akinetopsia – selective impairment of visual perception of motion („motion
blindness“), whilst there is a normal recognition of colors or object forms. Lesion
within extrastriatal cortex (dorsal stream, lateral TPO region).
- Prosopagnosia (not as rare as visual object agnosia) – loss of ability to recognize
familiar faces. It can be highly specific (for human faces, for own face, for animal
faces). Most often there is a lesion within right-sided occipitotemporal or
parietooccipital cortical regions (ventral stream).
Auditory agnosia
Very rare, usually is resulting from the lesion within the left-sided lateral temporal neocortex.
– Auditory agnosia for non-linguistic sounds (“psychic deafness“) (the inability
to recognize concrete sounds as animal noises, the sound of a stream of water, of a
sounding bell, of a ticking of a clock, etc.)
- Phonagnosia (auditory analog of prosopagnosia) – impairment of voice recognition and
discrimination; the inability to recognize familiar voice (lesion in lower and lateral
parts of the right parietal lobe) and to discriminate between unfamiliar voices
(impairment of the temporal lobes independently of the side). De facto 2 anatomical
systems – 2 distinct clinical syndromes.
- Sensory amusia – the inability to recognize music, melody or rhythms (lesion
within the non-dominant hemisphere)
Tactile agnosia
= astereognosia
A condition in which objects tactually are not recognized. The sensation had to be
intact.
Primary astereognosia – patient is neither able to tactually recognize objects
nor their forms or materials from which they are made.
Secondary astereognosia – Patient does not recognize tactually objects but
he/she recognizes well the form, size or material.
The most commonly lesion can be found within the parietal lobe behind the
postcentral gyrus (incl. supramarginal gyrus ). The disorder can be observed in
lesions within both dominant and non-dominant hemispheres.
Multisensorial agnosias
very rare
Disorders of somatognosia
- impairments of the recognition of the body scheme.
- Autotopagnosia – patient does not recognize parts of his/her own body. Disorder
is not related to the dominant/non-dominant hemisphere, it results from impairment
of contralateral parietal lobe.
- Hemisomatagnosia
- Finger agnosia – difficulty in distinguishing fingers on hand (this condition can be
seen in Gerstmann΄s syndrome).
- Mirror asomatognosia – mirror-induced disorders of the body image. Right-sided
lesions.
- Agnosia of pain – pain asymbolia (Schilder-Stengel syndrome) – emotional
reactions to the pain are absent in the patient. Disorder is caused by the dysfunction
of parietal lobe.
Anosognosia
– inability tp recognise and to understand own physical disability (especially motor deficit hemiplegia) that is actually denying by the patient. Typically anosognosia can be seen in pts with
left-sided hemiplegia.
In fact the awareness of own deficit is lacking = disorder of focused attention!
Anton’s syndrome
simultaneous occurrence of cortical blindness and anosognosia (pt denies truthfull loss of vision)
Neglect syndrome – unilateral spatial agnosia
attentional hemideficit = selective unawareness of contralateral stimuli. Practically
pts with neglect syndrome “ignore“ contralateral stimuli and do not react to them.
Within neglect also there can be hemiakinesia (movement deficiency) and/or
anosodiaforia (absence of concomitant emotions for serious functional deficit).
– damage of large-scale cortico-subcortical neurocognitive network for directed
attention (right-sided inferior parietal lobule, right-sided prefrontal and orbitofrontal
cortex, right-sided thalamus and basal ganglia)
Dissociations between perception and
consciousness after brain damage
(conscious perception and unconscious /implicit, covert/ perception)
- Unconscious perception in neglect syndrome
There is increasing evidence that some pts with neglect may covertly perceive the contralateral stimuli and that
may at least partially react to these stimuli (Volpe et al. 1979; Berti et al. 1992; Wallace 1994)
- Covert recognition of faces in prosopagnosia
In some cases of prosopagnosia, there has been a dramatic dissociation between the loss of face recognition
ability on the one hand, and the apparently preserved ability to recognize faces, when that is assessed indirectly
– skin resistance (Bauer 1984; Bruyer 1992; DeHaan et al. 1987, 1992), ERP (Renault et al. 1989)
- Implicit shape perception in apperceptive visual agnosia
- Implicit object identification in associative visual agnosia
(Taylor and Warrington 1971; Goodale et al. 1991; Jankowiak et al. 1992; Farah and Feinberg 1997)
- Blindsight – the best known syndrome – preserved ability of some patients to respond to certain aspects of
visual stimuli in the areas of their visual fields that are blind on conventional clinical testing (lesions of prim.
visual cortex). (Riddoch 1917; Weiskrantz et al. 1974, 1977, 1996, 1998; Perenin 1987; Ptito et al. 1991; Stoerig
and Cowey 1992; Tomaiuolo et al. 1997; Sahraie et al. 1997; Zeki and ffytche 1998)
- Inverse Anton’s syndrome - pt. with spared central island of vision denies visual sensation and he/she
is behaving as the blind = selective impairment of awareness for visual stimuli in complete visual field (covert
vision). (Walsh and Hoyt 1969; Hartmann et al. 1991; Brázdil et al. 2000)
Determination of hemispheric
dominance
Interview about writing, eating with spoon, throwing a ball, kicking,
step; tapping – domin. hand 50/min, nondomin. hand 45/min.
Left hemisphere is dominant in 95% right-handers and 60% lefthanders!
Left hemisphere – dominant for speech and motor
functions, reading, writing, counting, recognition of colors,
verbal memory, important for linguistic thinking, ...
Right hemisphere – dominant for attentional functions,
prosopognosia, prosodia (affective component of speech),
nonverbal communication (ability to „read from face“),
visuo-spatial perception, visual and topographical
memory, recognition of music, …
Drug-induced mental disorders
Quite frequent, especially in elderly patients (mostly
they are caused by pharmacological polytherapy)
Depression, delirium, psychosis, agitation,
aggression
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Digitalis
Corticosteroids
Indomethacine
Phenacetine
Phenylbutazone
Cimetidine
Benzodiazepines
Captopril
Propranolol
Niphedipin
PNC
Cephalosporines
Oral contraceptives
Vincristine
• Carbamazepine
• Phenytoine
• Primidone
• Topiramate
• Clobazam
• Phenobarbital
• Levodopa
• Amantadine
• Anticholinergics
• Thyroxine
• Interferone
• …..
; score > 24 normal; < 24 suggests dementia