Overview of Brain Anatomy and function

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Overview of Brain Anatomy and function

• Wei-Ching Lee, M.D.

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INTRODUCTION

• Lobes
• Frontal
• Parietal
• Temporal
• Occipital
• Brainstem

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Anatomy
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Anatomy
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Homunculus Man
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Circle of Willis
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Gold ACAPink MCABlue PCA
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Frontal Lobe

• Conscientiousness
• Judgments
• How we initiate activity in response to our
  environment.
• Controls our emotional response.
• Controls our expressive language.
• Assigns meaning to the words we choose (abstract
  thought)
• Attention span
• Involves word associations (language planning)
• Memory for habits and motor activities (short
  term memory)
• Motor cortexVoluntary movement
• Impulse control
• Perseverance

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Frontal Lobe DeficitProblems

• Loss of simple movement of various body parts
  (Paralysis).
• Inability to plan a sequence of complex movements
  needed to complete multi-stepped tasks, such as
  making coffee (Sequencing).
• Loss of spontaneity in interacting with others.
• Loss of flexibility in thinking.
• Persistence of a single thought (Perseveration).
• Inability to focus on task (Attending).
• Mood changes (Emotionally Labile).
• Changes in social behavior.
• Changes in personality.
• Difficulty with problem solving.
• Inablility to express language (Broca's Aphasia).

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Parietal Lobe Function

• Location for visual attention.
• Location for touch perception.
• Goal directed voluntary movements.
• Manipulation of objects.
• Integration of different senses that allows for
  understanding a single concept.

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Parietal LobeProblems resulting from deficit

• Inability to attend to more than one object at a
  time.
• Inability to name an object (Anomia).
• Inability to locate the words for writing
  (Agraphia).
• Problems with reading (Alexia).
• Difficulty with drawing objects.
• Difficulty in distinguishing left from right.
• Difficulty with doing mathematics (Dyscalculia).
• Lack of awareness of certain body parts and/or
  surrounding space (Apraxia) that leads to
  difficulties in self-care.
• Inability to focus visual attention.
• Difficulties with eye and hand coordination.

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Temporal Lobe Function

• Hearing ability
• Memory acquisition
• Some visual perceptions
• Categorization of objects.

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Temporal Lobe DeficitsProblems

• Difficulty in recognizing faces (Prosopagnosia).
• Difficulty in understanding spoken words
  (Wernicke's Aphasia).
• Disturbance with selective attention to what we
  see and hear.
• Difficulty with identification of, and
  verbalization about objects.
• Short-term memory loss.
• Interference with long-term memory
• Increased or decreased interest in sexual
  behavior.
• Inability to catagorize objects (Catagorization).
  
• Right lobe damage can cause persistant talking.
• Increased aggressive behavior.

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Occipital Lobe Function

• Vision

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Occipital Lobe Deficits--Problems

• Defects in vision (Visual Field Cuts).
• Difficulty with locating objects in environment.
• Difficulty with identifying colors (Color
  Agnosia).
• Production of hallucinations
• Visual illusions - inaccurately seeing objects.
• Word blindness - inability to recognize words.
• Difficulty in recognizing drawn objects.
• Inability to recognize movement of an object
  (Movement Agnosia).
• Difficulties with reading and writing.

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Cerebellum Function

• Coordination of voluntary movement
• Balance and equilibrium
• Some memory for reflex motor acts.

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Cerebellum DeficitsProblems

• Loss of ability to coordinate fine movements.
• Loss of ability to walk.
• Inability to reach out and grab objects.
• Tremors.
• Dizziness (Vertigo).
• Slurred Speech (Scanning Speech).
• Inability to make rapid movements.

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Brainstem

• Midbrain
• Pons
• Medulla

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Brainstem Function

• Breathing
• Heart Rate
• Swallowing
• Reflexes to seeing and hearing (Startle
  Response).
• Controls sweating, blood pressure, digestion,
  temperature (Autonomic Nervous System).
• Affects level of alertness.
• Ability to sleep.
• Sense of balance (Vestibular Function).

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Brainstem DeficitsProblems

• Decreased vital capacity in breathing, important
  for speech.
• Swallowing food and water (Dysphagia).
• Difficulty with organization/perception of the
  environment.
• Problems with balance and movement.
• Dizziness and nausea (Vertigo).
• Sleeping difficulties (Insomnia, sleep apnea).

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Midbrain

• Function
• Body posture
• Equilibrium
• Autonomic Nervous System
• Blood pressure
• Temperature
• Emotional influence
• Reg appetite and hormones
• Nuclei of CN III and IV

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Midbrain lesion

• Variable LOC
• Abnormal extensor tone
• Hyperventilation
• CN III and IV deficits
• CN IV nerve lesion head tilted away from lesion
• CN IV nucleus lesion head tiled towards lesion
• CN III innervates all eyes muscles except LR6
  and SO4, eye deviated laterally and downward with
  eyelid down (levator palpebrae)

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Pons

• Function
• Respiration
• Chewing
• Taste
• Arousal, wakefulness, alertness
• Nuclei of CN V, VI, VII, VIII

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Pons lesion

• Semi-coma
• Abnormal extensor tone
• Apneusis
• Withdrawal
• CN V,VI, VII (facial colliculus syndrome)
• CN V ipsi jaw deviation upon opening
• VI diplopia, paralysis of ipsi LR but also
  inablity to turn contra eye medially
• VII cant close eye or smile

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Medulla

• Function
• Life-sustaining control center controls hear,
  respiration, vasomotor
• Cough, gag, swallow, vomit, digest
• Nuclei of CN VIII, IX, X, XI, XII

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Medulla Lesion

• Comatose
• Abnormal breathing
• Ataxic
• Absent gag reflex
• Absent cough
• CN VIII, IX, X, XI, XII deficits
• VIII ipsi stumbling but contra nystagmus
• IX, X, XI absent gag reflex, contra uvula
  deviation, dysphonia, dysphagia
• XII ipsi tongue deviation and atrophy

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Function of Hemispheres

• Right Hemisphere 
• judging the position of things in space
• knowing body position
• understanding and remembering things we do and
  see
• putting bits of information together to make an
  entire picture
• controls the left side of the body
• Left Hemisphere
• understanding and use of language (listening,
  reading, speaking and writing)
• memory for spoken and written messages
• detailed analysis of information
• controls the right side of the body

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Online references

• http//www.wisc-online.com/objects/index_tj.asp?ob
  jidOTA502
• http//www.neuroskills.com/edu/ceufunction1.shtml
• http//www.hopkinshospital.org/health_info/Neurolo
  gical20Diseases/Reading/brain_anatomy.html
• http//training.seer.cancer.gov/ss_module00_bbt/un
  it02_sec04_c_brain.html

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SAE

• Findings commonly seen after right hemisphere
  stroke include
• Right hemiplegia
• Aphasia
• Visual-Perceptual deficits
• Agraphia

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SAE

• Answer C
• Strokes on nondominant hemisphere present with
  contralateral hemiplegia and hemianesthesia,
  aprosody (absence of normal speech in pitch,
  rhythm, and variations in stress), visual spatial
  deficit, and neglect syndrome.

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SAE

• In TBI, MRI is preferred to CT scan in the
• Eval of acute brain injury
• Detection of SAH
• Detection of epidural hematomas
• Eval of diffuse axonal injury

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SAE

• Answer D
• MRI is considered better than CT for evaluating
  DAI. CT is superior to MRI for detection of acute
  extra-axial hematomas, and in the eval of acute
  brain injury

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SAE

• 74 y/o woman has had a stroke with left
  hemiparesis and left neglect. Muscle tone is
  increased, and flexion contractures are beginning
  to develop in her left elbow, wrist, and hand.
  Initial intervention would be
• Diazepam 2.5mg tid
• Neurolytic block to median nerve
• Botulinum toxin injection to forearm flexors
• Static muscle stretch
• Baclofen 5mg qid

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SAE

• Answer D.
• In treating spasticity, the approach with the
  least possible adverse effects should be used
  first. In this case, ROM, stretching, and
  positioning with splints would be the initial
  treatment.

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SAE

• Following a head injury, a 35 y/o W presents with
  vertigo. She reports a sensation of spinning
  beginning several seconds after standing up
  radiply, bending over, or rolling in bed.
  Symptoms lasts for approx 30 sec. Exam is notable
  for nystagmus during episodes of vertigo, normal
  extremity coordination, and min increase in sway
  during Romberg. Most likely dx is
• Benign positional vertigo
• Cerebellar contusion
• Unilateral vestibular paresis
• Bilateral vestibular paresis

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SAE

• Answer A.
• BPV characterized by transient episodes of
  vertigo precipitated by changes in position of
  the head. Treatment involves psecific otolith
  repositioning maneuver or seris of habituation
  exercises.