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Anatomy

Central Nervous System

Question 161 of 180

Which of the following clinical features would you LEAST expect to see in a lesion of the frontal lobe:

Answer:

Loss of two-point discrimination is most likely to occur in a lesion of the parietal lobe. Expressive dysphasia results from damage to Broca's area. Contralateral weakness of the face and arm results from damage to the primary motor cortex. Personality change results from damage to the prefrontal cortex. Conjugate eye deviation towards side of lesion results from damage to the frontal eye field.

The frontal lobe extends from the central sulcus to the frontal pole. It is separated from the parietal lobe posteriorly by the central sulcus and from the temporal lobe inferoposteriorly by the lateral sulcus.

By BruceBlaus (Own work) [CC BY 3.0 , via Wikimedia Commons

Lobes of the Brain. (Image by BruceBlaus (Own work) [CC BY 3.0 , via Wikimedia Commons)

Function

Areas of the frontal lobe are responsible for:

  • Movement (planning and execution)
  • Higher intellect, problem solving and judgement
  • Attention and concentration
  • Behaviour, personality and mood
  • Language production
  • Continence

Cortical Areas

Table: Cortical Areas of the Frontal Lobe

Area Function Lesion
Primary motor cortex Contralateral movement of voluntary muscles Contralateral UMN weakness/paralysis
Premotor cortex Role in coordination of complex movements  Apraxia, UMN signs
Supplementary motor cortex Role in programming complex motor sequences  Inability to plan sequence of complex movements
Frontal eye field Conjugate deviation of the eyes to the opposite side Conjugate deviation of the eyes towards the side of the lesion (and away from the side of weakness)
Broca speech area (dominant hemisphere) Speech production Expressive dysphasia
Prefrontal cortex Higher intellect, problem-solving, judgement, personality, emotion and mood, central control of micturition Inappropriate social behavior, difficulty in adaptation and loss of initiative, primitive reflexes, inability to concentrate, incontinence

  • The primary motor cortex is located in the precentral gyrus and is responsible for voluntary movements of muscles of the opposite side of the body.
  • The premotor cortex plays a role in the control and coordination of proximal and axial muscles, it prepares the motor cortex for specific movements in advance of their execution.
  • The supplementary motor cortex is concerned with programming of complex movements and regulates somatosensory input into the motor cortex.
  • The Broca speech area (in the dominant hemisphere only) is the 'expressive' centre for the production of speech. It is connected to the Wernicke speech area by the arcuate fasciculus.
  • The frontal eye field is involved in making eye movements to the contralateral side.
  • The prefrontal cortex governs personality, emotional expression, initiative and the ability to plan.
  • The cortical micturition centre, within the prefrontal cortex, is involved in the cortical inhibition of the voiding of the bladder.

By Blausen.com staff. "Blausen gallery 2014, via Wikimedia Commons

Motor and Sensory Regions of the Cerebral Cortex. (Image by Blausen.com staff. “Blausen gallery 2014, via Wikimedia Commons)

Blood Supply

The blood supply to the frontal lobe is from the anterior cerebral artery (supplying the medial surface of the primary motor cortex which controls the lower limb) and the middle cerebral artery (supplying the lateral surface of the primary motor cortex which controls the face and upper limb).

By derivative work: Frank Gaillard (talk) Brain_stem_normal_human.svg: Patrick J. Lynch, medical illustrator (Brain_stem_normal_human.svg) [GFDL 1.3 (www.gnu.org/licenses/fdl-1.3.html), GFDL 1.3 (www.gnu.org/licenses/fdl-1.3.html), CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

Cerebral Blood Supply. (Image by derivative work: Frank Gaillard (talk) Brain_stem_normal_human.svg: Patrick J. Lynch, medical illustrator (Brain_stem_normal_human.svg) [GFDL 1.3 (www.gnu.org/licenses/fdl-1.3.html), via Wikimedia Commons)

Clinical Implications

Damage to the frontal lobe may cause a diverse range of presentations including:

  • contralateral weakness/paralysis in an UMN pattern (damage to the primary motor cortex)
  • inability to plan sequence of complex movements (damage to the premotor cortex and supplementary motor cortex)
  • conjugate eye deviation where both eyes look towards the side of the lesion and away from the side of weakness (damage to the frontal eye field)
  • expressive dysphasia (damage to the Broca speech area)
  • personality, mood and behavioural change with loss of initiative and inability to problem solve (damage to the prefrontal cortex)
  • primitive reflexes (damage to the prefrontal cortex)
  • anosmia (damage to the olfactory tract as a result of close proximity to inferior frontal lobe)
  • incontinence (damage to the cortical micturition centre)

Cortical Language Areas. (Image by Peter Hagoort [CC BY 3.0 , via Wikimedia Commons)

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  • Biochemistry
  • Blood Gases
  • Haematology
Biochemistry Normal Value
Sodium 135 – 145 mmol/l
Potassium 3.0 – 4.5 mmol/l
Urea 2.5 – 7.5 mmol/l
Glucose 3.5 – 5.0 mmol/l
Creatinine 35 – 135 μmol/l
Alanine Aminotransferase (ALT) 5 – 35 U/l
Gamma-glutamyl Transferase (GGT) < 65 U/l
Alkaline Phosphatase (ALP) 30 – 135 U/l
Aspartate Aminotransferase (AST) < 40 U/l
Total Protein 60 – 80 g/l
Albumin 35 – 50 g/l
Globulin 2.4 – 3.5 g/dl
Amylase < 70 U/l
Total Bilirubin 3 – 17 μmol/l
Calcium 2.1 – 2.5 mmol/l
Chloride 95 – 105 mmol/l
Phosphate 0.8 – 1.4 mmol/l
Haematology Normal Value
Haemoglobin 11.5 – 16.6 g/dl
White Blood Cells 4.0 – 11.0 x 109/l
Platelets 150 – 450 x 109/l
MCV 80 – 96 fl
MCHC 32 – 36 g/dl
Neutrophils 2.0 – 7.5 x 109/l
Lymphocytes 1.5 – 4.0 x 109/l
Monocytes 0.3 – 1.0 x 109/l
Eosinophils 0.1 – 0.5 x 109/l
Basophils < 0.2 x 109/l
Reticulocytes < 2%
Haematocrit 0.35 – 0.49
Red Cell Distribution Width 11 – 15%
Blood Gases Normal Value
pH 7.35 – 7.45
pO2 11 – 14 kPa
pCO2 4.5 – 6.0 kPa
Base Excess -2 – +2 mmol/l
Bicarbonate 24 – 30 mmol/l
Lactate < 2 mmol/l

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