Frontal Lobe Syndromes
The frontal lobes of the brain have enlarged greatly during phylogeny; their diverse connections with the basal ganglia, basal forebrain, and
cerebellum, as well as other cortical areas, reflect their multiple motor and behavioral functions. Damage to the frontal lobes may produce a variety of clinical signs, most frequently changes in behavior. Such changes may easily be overlooked with the traditional neurological examination, although complained of by patient’s relatives, and hence specific bedside tests of frontal lobe function should be utilized, for example:
- Verbal fluency: e.g., letter/phonemic (F, A, S) probably a more spe- cific test than category/semantic (animals, foods).
- Proverb interpretation: e.g., "Make hay while the sun shines"; "Too many cooks spoil the broth"; interpretation tends to be con- crete in frontal lobe disorders.
- Cognitive estimates: e.g., height of the Post Office Tower, length of a man’s spine, distance from London to Edinburgh; may be grossly abnormal or inappropriate.
- Copying motor sequences, to assess motor programming ability:
e.g., Luria fist-edge-palm test (three step motor sequence with hand).
- Alternating sequence tests: e.g., alternating finger flexion/extension out of phase in two hands, or repeatedly writing m n m n m n (also used as tests of praxis, which may be affected with frontal lobe pathology); swapping a coin from hand to hand behind back in a predictable pattern and asking the patient which hand the coin is in.
- Set-shifting or go/no go tests, in which an alternating pattern is suddenly changed, e.g., changing the previously predictable (left/right) pattern of coin hidden in clenched hand swapped over behind back; rhythmic tapping with pen on a surface (I tap once, you tap twice; I tap twice, you tap once); tests of response inhibi- tion (ask patient to clap three times, s/he does so multiple times).
A useful clinico-anatomical classification of frontal lobe syndromes which reflects the functional subdivisions of the frontal lobes is as follows:
- Orbitofrontal Syndrome ("disinhibited"):
Disinhibited behavior (including sexual disinhibition), impulsivity
Inappropriate affect, witzelsucht, euphoria Emotional lability (moria)
Lack of judgment, insight
Distractibility, lack of sustained attention; hypermetamorphosis Motor perseverations are not a striking feature
- Frontal Convexity Syndrome ("apathetic"): Apathy; abulia, indifference
Difficulty set-shifting, stimulus boundedness Reduced verbal fluency
Deficient motor programming, e.g., three step hand sequence, rhythmical tapping (go/no-go test)
- Medial Frontal Syndrome ("akinetic"):
Little spontaneous movement, bradykinesia, hypokinesia Sparse verbal output (akinetic mutism)
Urinary incontinence Sensorimotor signs in lower limbs Indifference to pain
Overlap between these regional syndromes may occur.
A "dysexecutive syndrome" has also been defined, consisting of difficulty planning, adapting to changing environmental demands (impaired cognitive flexibility, e.g., in set-shifting tests), and directing attentional resources. This may be seen with dorsolateral (prefrontal) damage.
These frontal lobe syndromes may be accompanied by various neurological signs (Frontal Release Signs or primitive reflexes). Other phenomena associated with frontal lobe pathology include imitation behaviors (echophenomena) and, less frequently, utilization behavior, features of the environmental dependency syndrome.
Larner AJ, Leach JP. Phineas Gage and the beginnings of neuropsychology. Advances in Clinical Neuroscience & Rehabilitation 2002; 2(3): 26 Parkin AJ. Explorations in cognitive neuropsychology. Hove: Psychology Press, 1996: 220-242
Trimble MR. Biological psychiatry (2nd edition). Chichester: Wiley, 1996: 147-156
Abulia; Akinesia; Akinetic mutism; Apathy; Attention; Disinhibition; Dysexecutive syndrome; Emotionalism, Emotional lability; Frontal Release Signs; Hypermetamorphosis; Hyperorality; Hyperphagia; Hypersexuality; Incontinence; Perseveration; Utilization behavior; Witzelsucht