neurology
TABLE OF CONTENTS
- Embryology
- Cellular Function
- Ascending Spinal Cord Tracts
- Descending Spinal Cord Tracts
- Brainstem Anatomy
- Cerebral Cortex
- Radiculopathy
- Spinal Cord Syndromes
- Invasive Spinal Cord Disease
- Demyelinating Disease
- Conduction Physiology
- Neuromuscular Junction (NMJ)
- Cranial Nerves 1-6
- Cranial Nerves 7-12
- Vision Neurology
- Auditory Sensation
- Vertigo
- Pediatric Brain Tumors
- Adult Primary Brain Tumors
- Ischemic Cerebrovascular Accidents
- Aneurysms and Intracranial Hemorrhage
- Cerebellum and Ventricles
- Diencephalon
- Basal Ganglia
- Neurotransmitter Activity in Psychiatric Disease
- Dementia
- Headache
- Seizures
- Traumatic Brain Injuries
EMBRYOLOGY
A. Notochord
- Derived from mesoderm.
- Induces ectoderm to form neuroectoderm at ~2.5 weeks gestation.
B. Neural Tube
- Arises from medial ectoderm.
- Fuses dorsally to form the neural tube at ~3 weeks gestation.
C. Meninges
- Dura Mater:
- Derived from mesoderm.
- Arachnoid Mater:
- Comes from neural crest cells.
- Pia Mater:
- Also derived from neural crest cells.
- Epidural Space:
- Associated with epidural anesthesia and hematomas.
- Subdural Space:
- Contains potential space for subdural hematomas.
- Subarachnoid Space:
- Contains cerebrospinal fluid (CSF).
- Involvement in lumbar punctures and hemorrhage.
D. Origins of Nervous Tissue
Forebrain/Prosencephalon:
- Diencephalon: Hypothalamus, thalamus, pineal gland.
- Telencephalon: Cerebral hemispheres, basal ganglia.
Midbrain/Mesencephalon:
- Midbrain structures.
Hindbrain/Rhombencephalon:
- Metencephalon: Cerebellum, pons.
- Myelencephalon: Medulla oblongata.
E. Neural Tube Defects
- Anencephaly:
- Caused by failure of rostral neuropore closure, leads to fatal absence of forebrain.
- Lissencephaly:
- Characterized by absent cortical sulci and gyri.
- Spina Bifida:
- Occulta: Vertebral defect with skin manifestations.
- Meningocele: Meninges through defect.
- Myelomeningocele: Spinal cord through defect, associated with Chiari II malformations.
CELLULAR FUNCTION
A. Neuronal Cells
Schwann Cells (PNS):
- One cell myelinates one axon.
- Derived from neural crest cells, S100 positive.
- Effective in Wallerian degeneration and regeneration.
- Relevant conditions: GBS, acoustic neuroma.
Oligodendrocytes (CNS):
- One cell myelinates multiple axons.
- From neuroectoderm, ineffective in regeneration.
- Associated with MS, PML, oligodendroglioma.
Astrocytes:
- Maintain blood-brain barrier.
- From neuroectoderm, GFAP marker.
- Associated with glioblastoma multiforme.
Microglia:
- CNS phagocytes, from mesoderm, involved in HIV-associated dementia.
B. Neuronal Anatomy
- Soma: Contains organelles, Nissl substance (rough endoplasmic reticulum).
- Axon: Delivers action potentials.
- Dendrites: Receives signals, contains Nissl substance.
- Neuron Injury: Cellular edema, peripheral nucleus, chromatolysis.
C. Wallerian Degeneration
PNS:
- Axonal retraction keeps proximal axonal membrane.
- Schwann cells break down myelin, facilitating regeneration.
- Macrophages clear debris.
CNS:
- Oligodendrocytes poorly manage debris and regeneration.
- Macrophages must cross the blood-brain barrier.
D. Sensory Receptors
- Aδ and C fibers: Responsible for pain transmission.
- Meissner Corpuscles: Senses fine touch and vibration.
- Pacinian Corpuscles: Detect pressure and high-frequency vibrations.
ASCENDING SPINAL CORD TRACTS
A. Spinothalamic Tract
Lateral Spinothalamic: Pain, temperature.
- Decussates 1-2 levels above.
Anterior Spinothalamic: Crude touch, pressure.
B. Dorsal Column-Medial Lemniscus
- Decussates at medulla, conveys fine touch and proprioception.
- Fasciculus Gracilis: T6 and below.
- Fasciculus Cuneatus: T5 and above.
C. Spinocerebellar Tract
- Delivers unconscious proprioception, ipsilateral to the cerebellum.
DESCENDING SPINAL CORD TRACTS
A. Corticospinal Tract
- Lateral Corticospinal: Voluntary movement, decussates at the inferior medulla.
- Anterior Corticospinal: Remains ipsilateral until termination at specific cervical and thoracic levels.
B. Corticobulbar Tract
- Leads to head and neck muscle control, innervates certain cranial nerves bilaterally and contralaterally.
BRAINSTEM ANATOMY
A. Midbrain
- Structures and Functions: CN III and IV nuclei, red nucleus, substantia nigra involved with motor functions.
B. Pons
- Contains CN V-VIII nuclei, reticular activating system, and longitudinal fasciculi.
C. Medulla
- Nuclei of CN VIII-XII, vital for autonomic control and reflexes.
CEREBRAL CORTEX
A. Frontal Lobe
- Contains primary motor cortex, areas for personality and speech regulation (Broca's area).
B. Temporal Lobe
- Involved in auditory processing (Wernicke's area) and memory.
C. Parietal Lobe
- Responsible for somatosensory processing and spatial orientation.
D. Occipital Lobe
- Primary visual processing center.
RADICULOPATHY
General Spinal Cord Function
- Anatomical considerations of spinal cord and common reflexes per level.
- Impingement effects and symptoms from nerve root involvement.
SPINAL CORD SYNDROMES
A. Anterior Cord Syndrome
- Typically due to anterior spinal artery occlusion, leads to bilateral loss of pain and temperature.
B. Brown-Sequard Syndrome
- Hemisection presents pain and temperature loss contralaterally, proprioception and motor function loss ipsilaterally.
C. Central Cord Syndrome
- Greater upper than lower extremity weakness; common in elderly with hyperextension injuries.
INFECTIOUS SPINAL CORD DISEASE
A. Tetanospasmin Toxin
- Binds to Renshaw cells; causes spastic paralysis classic findings.
B. Rabies Virus
- Retrograde transsynaptic transport to the CNS, hydrophobia as a hallmark.
C. Poliomyelitis
- Causes asymmetric flaccid paralysis in unvaccinated individuals.
DEMYELINATING DISEASE
A. Multiple Sclerosis
- Characterized by optic neuritis and neurological deficits; varied presentations like internuclear ophthalmoplegia.
B. Guillain-Barré Syndrome
- Ascending paralysis after GI infection, classic CSF findings.
CONDUCTION PHYSIOLOGY
A. Resting Potential
- Neuronal membrane potential, determined primarily by sodium and potassium ions.
B. Action Potential
- Depolarization followed by repolarization phases of neuronal firing.
NEUROMUSCULAR JUNCTION (NMJ)
A. Overview
- Communication between motor neurons and muscle fibers; neurotransmitter release and receptor activation.
CRANIAL NERVES
I - VI
- Overview, function, associated lesions and symptoms.
VISION
A. Pathway and Clinical Presentation
- From retina to visual cortex; common pathologies affecting this pathway.
AUDITORY
A. Basics
- Transport currents, anatomy of the auditory system, testing for hearing loss.
VERTIGO
A. Peripheral and Central Causes
- Presentation: positional vs spontaneous vertigo, clinical evaluations.
PEDIATRIC BRAIN TUMORS
Main Types
- Include Medulloblastoma, Astrocytoma, and Ependymoma along with clinical presentations.
ADULT PRIMARY BRAIN TUMORS
A. Classification
- Include Glioblastoma, Astrocytoma, Meningiomas among others, with typical lesions and presentations.
ISCHEMIC CEREBROVASCULAR ACCIDENTS
A. Classification
- Thrombotic, embolic, and watershed areas of infarcts.
HEMORRHAGIC CEREBROVASCULAR ACCIDENTS
Details
- Types of hematomas, clinical findings, diagnosis, and management strategies.
DYNAMIC ANATOMY OF BRAINSTEM
A. Functional Sites & Clinical Relevance
- Breakdown of roles and lesions associated with various cranial nerve nuclei, control pathways, and clinical symptoms.
SPINAL CORD DISEASES AND SYNDROMES
A. Definitions
- Overview and symptoms of various spinal cord syndromes affecting motor and sensory functions.
CONCLUSIONS
- Summation of critical points and clinical correlations to guide further study into neurology and associated pathologies.