Frontal lobe

Frontal Lobe

-Dr. Sachin A Adukia

Frontal Lobe

Largest of all lobes Sagitally : ~ 1/3rd of the cerebral

hemisphere

3 major areas in each lobe Dorsolateral aspect Medial aspect Inferior orbital aspect

Lateral surface frontal lobe

Precentral sulcus – parallel to central sulcus, between them precentral

gyrus

Sup and inf frontal sulci divide sup, middle and inf frontal gyri

Medial surface Frontal lobe

Between cingulate sulcus and superior medial margin of hemisphere Posterior part vertical sulcus – paracentral lobule

Orbital surface Frontal lobe

Divided into four orbital gyri by a well-marked H-shaped orbital sulcus.

The medial, anterior, lateral, and posterior orbital gyri.

the olfactory sulcus, for the olfactory tract;

the portion medial to this is named the straight gyrus, and is continuous with the superior frontal gyrus on the medial surface.

Vascular supply

Medial parts of frontal lobe: Anterior cerebral artery

Convexity : Superior (rolandic) division of MCA

Inferior surface: ACA and MCA

Underlying deep white matter: penetrating arteries (lenticulostriate) from stem of MCA

Primary Motor CortexPrecentral gyrus; Brodmann’s Area 4

Input thalamus, BG, sensory, premotor

Output motor fibers to brainstem and spinal cord

Function executes design into movement

Lesions / tone; power; fine motor function on

contralateral side

Bedside tests

1. Motor strength of hand grip. The patient is asked to grip the examiners fingers. Strength should be roughly equal, with greater strength on

the dominant side. It should be difficult for the examiner to free her/his fingers.

2. Motor speed as in finger tapping; but does not discriminate from the premotor cortex.

poor performances suggest local lesions - vascular or neoplastic generalized lesion - degenerative disease

Pre Motor CortexSup. Frontal gyrus Lat. Surface; Brodmann Area

6,8Input

thalamus, BG, sensory cortex Output

primary motor cortexFunction

Planning complex movements; controls coarse postural movements

Lesions moderate weakness in proximal muscles on

contralateral side

1. Sensorimotor abilities asking the patient touch each finger to the thumb in

succession as rapidly as possible. Watch for speed and dexterity.

2. Apraxia to demonstrate the use of a shovel.

Supplementary Motor CortexSup. Frontal gyrus Med. Surface; Brodmann’s area 6,8

Input cingulate gyrus, thalamus, sensory & prefrontal cortex

Output premotor, primary motor

Function intentional preparation for movement; procedural

memoryLesions

mutism, akinesia

Frontal eye fieldsMiddle Frontal Gyrus; Broadman’s area 8

Input parietal / temporal (ventral = what is target) posterior parietal cortex (dorsal = where is target)

Output caudate; superior colliculus; PPRF

Function executive: selects target and commands movement

(saccades)Lesion

eyes deviate ipsilaterally with destructive lesion contralaterally with irritating lesions

Voluntary eye movements are of two types. Pursuit. Saccades.

Bedside test: 1. Ask the patient to follow the movement of a finger

from left to right and up and down. 2. Ask the patient to look from left to right, up and

down (with no finger to follow). Note inability to move or jerky movement.

Broca’s speech areaInf. Frontal Gyrus (Pars Triangularis &Pars Opercularis)

Brodman’s area 44,45

Input Wernicke’s

Output primary motor cortex

Function speech production (dominant hemisphere);

emotional, melodic component of speech (non-dominant)

Lesions motor aphasia; monotonous speech

Asymmetry of the Frontal Lobes

Left Language Encoding memories

Right Nonverbal movements, facial expression Retrieving memories

Functional Frontal Lobe Anatomy

Five ‘frontal sub cortical circuits’

1. Motor2. Oculomotor3. Dorsolateral prefrontal4. Lateral orbitofrontal5. Anterior cingulate

1. Frontal subcortical Motor Circuit

Supplementary Motor & Premotor : planning, initiation & storage of motor programs; fine-tuning of movements

Motor : final station for execution of the movement according to the design

SMA,Premoto

r,Motor

Caudate

Globus Pallidus

Thalamus

VL,VA,CM

Hypo-thalamu

s

2.Frontal Oculomotor Circuit

Voluntary scanning eye movement Independent of visual stimuli

Frontal Eye field

Central Caudate

DM Globus Pallidus &Substantia

Nigra

ThalamusVA, MD

3.Dorsolateral Prefrontal Circuit

Executive functions: motor planning, deciding which stimuli to attend to, shifting cognitive sets Attention span and working memory

Lateral Pre-

Frontal

DLCaudat

e DM

Globus Pallidus

&Substantia Nigra

Thalamus

VA, MD

4. Lateral Orbitofrontal Circuit

Emotional life and personality structure

Infero-Lateral

Pre-Frontal

VMCaudate

DM Globus

Pallidus &Substantia Nigra

ThalamusVA, MD

Orbito-Frontal

5. Anterior Cingulate Circuit

Abulia, akinetic mutism

MDThalamus

Ant. Cingulate

Ventral Striatum

Globus Pallidus &Substantia

Nigra

ThalamusMD

Symptoms of Frontal Lobe Lesions

Disturbances of Motor Function Loss of fine movements, speed, and strength

Typically appears after damage to the primary motor cortex

Changes in voluntary gaze Damage to frontal eye field

Change in speech Motor aphasia; dysprosody (monotonous speech) Speech is sparse, slow, hesitant, disturbance of

rhythm and articulation, difficulty in word finding, wrong words are chosen & often mispronounced, perseveration, agrammatism

telegraphic language

Dorsolateral prefrontal lobe syndrome Executive dysfunction.

Inability to organize & plan. Inability to initiate, stop and modify behavior

in response to changing stimuli. Impaired problem solving Inability to inhibit responses Perseveration & inability to shift thought

process Impaired fluency

Memory problems: Defective working memory. Defective retrieval.

Impaired attention. Lack of initiative & spontaneity. Impaired abstract thinking Impaired problem solving, creativity Impaired language & verbal fluency

Orbit frontal syndrome

Disinhibition and impulsivity of thought, affection and action

Failure to appreciate consequences of one’s action.

A flat affect, blunted emotional response. Imitation and utilization behavior Euphoria, hypomania, Grandiosity

Anterior cingulate syndrome

Akinetic mutism

Represents a wakeful state of profound apathy, with indifference to pain, thirst & hunger and absence of motor & psychic initiative.

Manifested by lack of spontaneous movement, absent verbalization and failure to respond to questions & commands

Abulia -- similar but less severe , lack of spontaneity, apathy, and

paucity of speech and movement

Phineas Gage (1848)

Bilateral Frontal lobe lesion

1. Apathy, Abulia, akinetic mutism, 2. Impulsiveness and irritability3.  Inability to sustain attention4.  gait disturbances5.  Sphincter disturbance6. Active learning, problem solving, judgment:-

impaired7.  Frontal release sign

a.   Snoutb.   Suckc.   Palmomentald.  Graspe.   Brow tapping

Frontal Assessment Battery

1. Similarities (conceptualization)

2. Lexical fluency (mental flexibility)

3. Motor series “Luria” test (programming)

4. Conflicting instructions (sensitivity to interference)

5. Go–No Go (inhibitory control)

6. Prehension behavior (environmental autonomy)

Interpreting results

A cut off score of 12 out of 18 on the FAB has a sensitivity of 77% and

specificity of 87% in differentiating between frontal dysexecutive type

dementias and DAT

Similarities (conceptualization)

“In what way are they alike?” A banana and a orange

(In the event of total failure: “they are not alike” or partial failure “both have a peel”, help the patient by saying “both a banana and an orange are….”; but credit 0 for the item; do not help the patient for the two following items)

A table and a chair A tulip, a rose, and a daisy

Score: only category responses (fruits, furniture, flowers) are considered correct. Three correct: 3 Two correct: 2 One correct: 1 None correct: 0

Lexical fluency (mental flexibility) Say as many words as you can beginning with the letter ‘S,’ any words except surnames or proper nouns.”

If the patient gives no response during the first 5 seconds, say:" for instance, snake.” If the patient pauses 10 seconds, stimulate him by saying: “any word beginning with the letter ‘S.’ The time allowed is 60 seconds.

Score (word repetitions or variations [shoe, shoemaker], surnames, or proper nouns are not counted as correct responses) More than nine words: 3 Six to nine words: 2 Three to five words: 1 Less than three words: 0

Controlled oral word association test (COWAT)

Motor series (programming)

“Look carefully at what I’m doing.”

The examiner performs alone three times with his left hand the series of Luria “fist–edge–palm.” “Now, with your right hand do the same series, first with me, then alone.” The examiner performs the series three times with the patient, then says to him/her: “Now, do it on your own.”

Score six correct consecutive series alone: 3 at least three correct consecutive series alone: 2 fails alone, but performs 3 correct consecutive series with

examiner: 1 cannot perform 3 correct consecutive series even with the

examiner: 0

Conflicting instructions (sensitivity to interference)

“Tap twice when I tap once.”

To be sure that the patient has understood the instruction, a series of three trials is run: 1-1-1.

“Tap once when I tap twice.”

To be sure that the patient has understood the instruction, a series of three trials is run: 2-2-2.

The examiner performs the following series: 1-1-2-1-2-2-2-1-1-2.

Score

No error: 3

One or two errors: 2

More than two errors: 1

Patient taps like the examiner at least four consecutive times: 0

Go–No Go (inhibitory control)

“Tap once when I tap once.”To be sure that the patient has understood the instruction, aseries of three trials is run: 1-1-1.

“Do not tap when I tap twice.”To be sure that the patient has understood the instruction, a

series of 3 trials is run: 2-2-2. The examiner performs thefollowing series: 1-1-2-1-2-2-2-1-1-2.

Score No error: 3 One or two errors: 2 More than two errors: 1 Patient taps like the examiner at least four

consecutive times: 0

Prehension behavior (environmental autonomy) “Do not take my hands.”

The examiner is seated in front of the patient. Place the patient’s hands palm up on his knees. Without saying anything or looking at the patient, the examiner brings his hands close to the patient’s and touches the palms of both the patient’s hands

If the patient takes the hands, the examiner will try again after asking him/her: “Now, do not take my hands.”

Score Patient does not take the examiner’s hands: 3 Patient hesitates and asks what he/she has to do: 2 Patient takes the hands without hesitation: 1 Patient takes the examiner’s hand even after he/she has

been told not to do so: 0

Post Graduates (in) Medicine Learning Some Concepts

P Prehension OrbitofrontalG Go-No-Go “M Motor series dorsolateralL Lexical fluency “S similarities “C Conflicting insturctns “

History in frontal lobe pathology

Personality changes (over familiar, tactless and sexual indiscretions)

Hyperorality Distractibility Poor motivation Inability to adapt to new situations Poor problem solving skills

Tests at bedsideAbstract thinking: Proverb interpretation

FAB

Cognitive estimates “What is the height of an average woman”?

Primitive reflexes

Neurological test Check for anosmia (olfactory nerve involvement)

Motor aphasia (Broca’s area involvement)

Formal Tests• Wisconsin Card Sorting Test• Trail Making• Stroop Color & Word Test• Tower of London Test

• Block design • Maze lest

Wisconsin Card Sorting Test

“Please sort the 60 cards under the 4 samples. I won’t tell you the rule, but I will announce every mistake. The rule will change after 10 correct placements.”

Used to assess the following "frontal" lobe functions: • strategic planning, • organized searching, • shift cognitive sets, • directing behavior toward a goal• modulating impulsive responding.

Trail Making Test

A

C12

73 D

5 B4

6

Various levels of difficulty:1. “Please connect the letters in alphabetical order as fast as you can.”2. “Repeat, as in ‘1’ but alternate with numbers in increasing order”

• visual search speed

• scanning,

• speed of processing,

• mental flexibility,

• executive functioning.

Stroop Color and Word TestsTo test attention, cognitive inhibiton

Lesion : Left ventro-lateral aspect of frontal / orbito-frontal

RED BLUE ORANGE YELLOW GREEN RED PURPLE REDGREEN YELLOW BLUE REDYELLOW ORANGE RED GREEN BLUE GREEN PURPLE RED

“Please read this as fast as you can”

Tower of London TestsUse:for the assessment of executive functioning

(specifically planning)

Various levels of difficulty:e.g. “Please rearrange the balls on the pegs, so that each peg hasone ball only. Use as few movements as possible”

Frontal lobe epilepsy

Clinical Features Frequent seizure with clustering Brief stereotyped Nocturnal Sudden onset and cessation No psychic aura or postictal confusion Rapid evolution with awareness lost at onset Prominent complex bilateral motor automatism involving

lower limbs Prominent ictal posturing and tonic spasm Versive head and eye turning Bizarre automatism Frequent secondary generalization Status epilepticus common

Frontal lobe epilepsyEEG

May show no ictal or interictal abnormality May show bilateral spike waves May show focal changes often widespread

Imaging/ pathology Hemartoma Benign tumors Gliomas Angioma Dysplasia Post traumatic Atrophy Tuberculoma Cysticercosis

Frontal Lobe Syndrome Mimics

Bilateral Caudate nucleus lesion Globus pallidus lesion – Apathy and abuliaBilateral thalamic infarctionMS – Apathy and disinhibitionSubcortical strokeAdrenoleukodystrophyParkinson’s diseaseHuntington’s diseaseDepressionSchizophreniaOCD

Thank You