Integrating Test Data with other Clinical Information

Integrating Test Data with other Clinical Information • Three Important Principles – Avoid the Fallacy of Affirming the Consequent • because B often follows A, occurrence of B proves that A has occurred – Be Open Minded • generate as many reasonable explanations for what you see – Apply Occam’s Razor • “the most likely explanation for a pattern is the one that requires the least number of unlikely events to account for it “

Errors in Formulation Affirming the Consequent • Complains of memory change after MVA • Testing - diffuse pattern (moderate-severe deficits in attention, executive function, processing speed c/w traumatic brain injury) • MRI – subtle, diffuse changes in deep white matter

Additional History • No loss of consciousness in MVA • History of functional declines, sensory and motor changes in year prior to MVA • Testing 1 year later shows further declines • Neurologic examination shows abnormal nerve conduction consistent with multiple sclerosis

Errors in Formulation Keeping an Open Mind • • Acute onset word-finding deficits – no recent events History of worsening depression Neurologic exam normal Neuropsychological testing is normal except for severe impairment in confrontation naming with paraphasias • Imaging shows multiple lesions, one in right temporal lobe with fresh blood

Additional History • Left-handed • Strong family history of – left-handedness – early strokes • Findings consistent with hemorrhage of genetically-based, cavernous angioma (small tumor of vessel wall) in right, language dominant hemisphere • Depression is irrelevant in this context

Errors in Formulation ‘Occam’s Razor’ • • 54 yo. M with recent memory complaints Neurologic exam normal Normal neuroimaging Family is concerned about ‘early Alzheimer’s’

Additional History • Long-standing history of major depressive disorder • No family history of dementia • Trouble caring for home and finances after partner died 4 years ago • Recently ‘got lost’ standing in front of his house, recovered quickly • Continues to perform at high level at cognitively demanding job

Behavioral Geography of the Brain

• The human brain has – ~ 100 billion neurons in the human brain – ~100 trillion synaptic connections – ~3 million miles of axons in the human brain

Brain Orientation Anterior Posterior Superior Inferior Rostral Caudal Dorsal Ventral

Brain Orientation

Other definitions • • Lateral – to the side Medial (mesial) – toward the middle Proximal – areas of brain near to one another Distal – areas of the brain far from one another • Ipsilateral – structures on same side of the body • Contralateral – structures on opposite sides of body

Divisions of the Brain Major Division Subdivision Principal Structure Forebrain Telencephalon Cerebral Cortex Basal Ganglia Limbic System Diencephalon Thalamus Hypothalamus Midbrain Mesencephalon Tectum Tegmentum Hindbrain Metencephalon Cerebellum Pons Myelencephalon Medulla Oblongata

Hindbrain • Metencephalon – Cerebellum • Involved in aspects of learning and coordination of skilled or smooth movement • Posture, walking, equilibrium – Pons • Links cerebellum to cerebrum, relays information from cerebral hemispheres to cerebellum • Role in vision, balance, auditory processing • Mylelencephalon – Medulla • Regulates bp, heart rate, respiration, controls breathing, basic muscle tone

Midbrain • Mesencephalon – Tectum (roof) – Tegmentum (floor) • Controls responses to sight • Relay station of auditory and visual information • Motor control of some muscles

Forebrain • Diencephalon – Thalamus – hypothalamus • Telencephalon – Limbic System – Basal Ganglia – Cerebral Cortex

Diencephalon • Hypothalamus – Controls aspects of motivated (pleasure and pain) and regulatory bx • bodily functions, body temp, thirst, hunger • circadian rhythms • “master gland” – regulation and secretion of hormones • Thalamus – Gateway to cortex – Relay center for sensory information – Links nervous and endocrine system

Limbic system • Groups of structures in center of brain above brainstem – – – – amygdala hippocampus parahippocampal gyrus cingulate gyrus fornix septum olfactory bulbs • Maintains homeostasis • Emotional reactions needed for survival

Basal Ganglia • Collection of subcortical nuclei in forebrain – Caudate nucleus – Putamen – Globus pallidus • Structures involved in voluntary control of movement • Motor planning and programming for speech • Attention and alerting before a motor response

Cerebral Cortex

Blumenfeld, 2002

Brain anatomy

Brain anatomy