King's Applied Anatomy of the Central Nervous System of Domestic Mammals

GEOFF SKERRITT is an RCVS and European Specialist in Veterinary Neurology, and a Diplomate and former President of the European College of Veterinary Neurology. In 1997 Geoff was one of the founders of VetMRI, the first mobile veterinary MRI facility in Europe. He is the founder and former Director of ChesterGates Animal Referral Hospital, a leading multi-discipline veterinary referral centre in the UK. He began his career as a Lecturer in veterinary anatomy at the University of Liverpool, UK. Enthusiasm for neuroanatomy led to a developing interest in veterinary neurology and the establishment of neurology in the curriculum and clinics at the University of Liverpool School of Veterinary Science. Geoff is a popular speaker at meetings and congresses and has published widely in the subjects of veterinary neuroanatomy and neurology.

• Foreword xviiPreface xixAcknowledgement xxiAbout the Contributors xxiiiAbout the Companion Website xxv1 Arterial Supply to the Central Nervous System 1Arterial Supply to the Brain 11.1 Basic Pattern of the Main Arteries Supplying the Brain 11.2 Basic Pattern of Incoming Branches to the Cerebral Arterial Circle 11.3 Species Variations 21.4 Summary of the Significance of the Vertebral Artery as a Source of Blood to the Brain 51.5 Humane Slaughter 61.6 Rete Mirabile 7Superficial Arteries of the Spinal Cord 81.7 Main Trunks 81.8 Anastomosing Arteries 81.9 Segmental Arteries to the Spinal Cord 101.10 General Principles Governing the Distribution of Arteries below the Surface of the Neuraxis 101.11 The Deep Arteries of the Spinal Cord 101.12 The Problem of Pulsation 111.13 Arterial Anastomoses of the Neuraxis 112 The Meninges and Cerebrospinal Fluid 13Meninges 132.1 General Anatomy of the Cranial and Spinal Meninges 132.2 Anatomy of the Meninges at the Roots of Spinal and Cranial Nerves 142.3 The Spaces around the Meninges 142.4 Relationship of Blood Vessels to the Meninges 162.5 The Filum Terminale 162.6 The Falx Cerebri and Membranous Tentorium Cerebelli 16Cerebrospinal Fluid 162.7 Formation of Cerebrospinal Fluid 162.8 The Choroid Plexuses 162.9 Mechanism of Formation of Cerebrospinal Fluid 172.10 Circulation of Cerebrospinal Fluid 172.11 Drainage of Cerebrospinal Fluid 192.12 Functions of Cerebrospinal Fluid 202.13 Blood‐brain Barrier 212.14 Collection of Cerebrospinal Fluid 222.15 Clinical Conditions of the Cerebrospinal Fluid System 233 Venous Drainage of the Spinal Cord and Brain 25The Cranial System of Venous Sinuses 253.1 General Plan 253.2 The Components of the Dorsal System of Sinuses 273.3 The Components of the Ventral System of Sinuses 283.4 Drainage of the Cranial Sinuses into the Systemic Circulation 28The Spinal System of Venous Sinuses 293.5 General Plan 293.6 Connections to the Cranial System of Sinuses 293.7 Territory Drained by the Spinal System of Sinuses 293.8 Drainage of the Spinal Sinuses into the Systemic Circulation 29Clinical Significance of the Venous Drainage of the Neuraxis 303.9 Spread of Infection in the Head 303.10 Paradoxical Embolism 303.11 Venous Obstruction 303.12 Angiography for Diagnosis 314 The Applied Anatomy of the Vertebral Canal 33The Anatomy of Epidural Anaesthesia and Lumbar Puncture 334.1 The Vertebrae 334.2 Spinal Cord 334.3 Meninges 354.4 Lumbar Puncture 354.5 Epidural Anaesthesia in the Ox 354.6 Injuries to the Root of the Tail 36The Anatomy of the Intervertebral Disc 364.7 The Components of the Disc 364.8 Senile Changes 384.9 Disc Protrusion 384.10 Fibrocartilaginous Embolism 41Malformation or Malarticulation of Vertebrae 414.11 The ‘Wobbler Syndrome’ in the Dog 414.12 The Wobbler Syndrome in the Horse 414.13 Atlanto‐Axial Subluxation in Dogs 424.14 Anomalous Atlanto‐Occipital Region in Arab Horses 424.15 Other Vertebral Abnormalities in Dogs 425 The Neuron 43The Anatomy of Neurons 435.1 General Structure 435.2 The Axon 465.3 Epineurium, Perineurium and Endoneurium 505.4 The Synapse 515.5 Phylogenetically Primitive and Advanced Neurons 545.6 Axonal Degeneration and Regeneration in Peripheral Nerves 555.7 Regeneration and Plasticity in the Neuraxis 585.8 Stem Cells and Olfactory Ensheathing Cells 585.9 The Reflex Arc 595.10 Decussation: The Coiling Reflex 606 The Nerve Impulse 63Excitation and Inhibition 636.1 Ion Channels and Gating Mechanisms 636.2 The Membrane Potential 646.3 The Excitatory Postsynaptic Potential 646.4 The Inhibitory Postsynaptic Potential 676.5 The Receptor Potential 686.6 The End‐plate Potential 696.7 Summary of Decremental Potentials 706.8 The Action Potential 716.9 Concerning Water Closets 736.10 Transducer Mechanisms of Receptors 736.11 Astrocytes 766.12 Oligodendrocytes 766.13 Microglia 777 Nuclei of the Cranial Nerves 79GeneralPrinciples Governing the Architecture of the Nuclei of the Cranial Nerves 797.1 Shape and Position of the Central Canal 797.2 Fragmentation of the Basic Columns of Grey Matter 797.3 Development of an Additional Component; Special Visceral Efferent 807.4 The Cranial Nerves of the Special Senses 827.5 Summary of the Architectural Principles of the Nuclei of the Cranial Nerves 82Names, Topography and Functions of the Cranial Nerve Nuclei 827.6 Somatic Afferent Nucleus 827.7 Visceral Afferent Nucleus 857.8 Visceral Efferent Nuclei 857.9 Special Visceral Efferent Nuclei 867.10 Somatic Efferent Nuclei 86Reflex Arcs of the Nuclei of the Cranial Nerves 87Significance of the Nuclei of the Cranial Nerves in Clinical Neurology 888 Medial Lemniscal System 89Conscious Sensory Modalities, their Receptors and Pathways 898.1 Conscious Sensory Modalities 898.2 Peripheral Receptors of Touch, Pressure and Joint Proprioception 918.3 Pathways of Touch, Pressure and Joint Proprioception 92Clinical Conditions Affecting the Medial Lemniscal System 948.4 Effects of Lesions in the Dorsal Funiculus 94Pain Pathways 968.5 Peripheral Receptors of Pain 968.6 Spinothalamic Tract of Man 978.7 Spinothalamic Pathways in Domestic Mammals 1008.8 Spinocervical Tract (Spinocervicothalamic Tract) 1008.9 Species Variations in the Medial Lemniscal System 1008.10 Somatotopic Localisation 1018.11 Blending of Tracts in the Spinal Cord 1018.12 Summary of the Medial Lemniscus System 1019 The Special Senses 103Vision 1039.1 Neuron 1 1039.2 Neuron 2 1039.3 Neuron 3 103Hearing 1069.4 Neuron 1 1069.5 Neuron 2 1069.6 Neuron 3 106Balance 1079.7 Neuron 1 1079.8 Neuron 2 107Taste 1129.9 Neuron 1 1129.10 Neuron 2 1129.11 Neuron 3 112Olfaction Proper: The Sense of Smell 1139.12 Neuron 1 1139.13 Neuron 2 1149.14 Neuron 3 114Summary of the Conscious Sensory Systems 11710 Spinocerebellar Pathways and Ascending Reticular Formation 11910.1 Spinocerebellar Pathways 11910.2 Ascending Reticular Formation 119Spinocerebellar Pathways 12010.3 Hindlimbs 12010.4 Forelimbs 12210.5 Projections of Spinocerebellar Pathways to the Cerebral Cortex 12310.6 Functions of the Spinocerebellar Pathways 12410.7 Species Variations 124Ascending Reticular Formation 12410.8 Organisation 124Functions of the Ascending Reticular Formation 12810.9 Arousal 12810.10 Transmission of Deep Pain 12810.11 Summary of Spinocerebellar Pathways and Ascending Reticular Formation 13211 Somatic Motor Systems 135Somatic Efferent Neurons 13511.1 Motor Neurons in the Ventral Horn of the Spinal Cord 135Muscle Spindles 13711.2 Structure of the Muscle Spindle 13711.3 The Mode of Operation of the Muscle Spindle 13711.4 Role of Muscle Spindles in Posture and Movement 13911.5 Golgi Tendon Organs 13911.6 Muscle Tone 14011.7 Motor Unit 14111.8 Recruitment of Motor Units 14111.9 Summary of Ways of Increasing the Force of Contraction of a Muscle 142The Final Common Path 14211.10 Algebraic Summation at the Final Common Path 14211.11 Renshaw Cells 14211.12 Lower Motor Neuron 14211.13 Integration of the Two Sides of the Neuraxis 14312 Pyramidal System 145Pyramidal Pathways 14512.1 The Neuron Relay 145Feedback Pathways of the Pyramidal System 14812.2 Feedback of the Pyramidal System 148Comparative Anatomy of the Pyramidal System 14912.3 Species Variations in the Primary Motor Area of the Cerebral Cortex 14912.4 Species Variations in the Pyramidal System 15012.5 The Function of the Pyramidal System 150Clinical Considerations 15112.6 Effects of Lesions in the Pyramidal System 15112.7 Validity of the Distinction between Pyramidal and Extrapyramidal Systems 15213 Extrapyramidal System 153Motor Centres 15313.1 Nine Command Centres 15313.2 The Cerebral Cortex 15313.3 Basal Nuclei and Corpus Striatum 15413.4 Midbrain Reticular Formation 15513.5 Red Nucleus 15513.6 Mesencephalic Tectum 15513.7 Pontine Motor Reticular Centres 15613.8 Lateral Medullary Motor Reticular Centres 15613.9 Medial Medullary Motor Reticular Centres 15613.10 Vestibular Nuclei 156Spinal Pathways 15613.11 Pontine and Medullary Reticulospinal Tracts 15613.12 Rubrospinal Tract 15813.13 Vestibulospinal Tract 15913.14 Tectospinal Tract 15913.15 The Position in the Spinal Cord of the Tracts of the Extrapyramidal System 15913.16 Summary of the Tracts of the Extrapyramidal System 15914 Extrapyramidal Feedback and Upper Motor Neuron Disorders 161Feedback of the Extrapyramidal System 16114.1 Neuronal Centres of the Feedback Circuits 16114.2 Feedback Circuits 16114.3 Balance between Inhibitory and Facilitatory Centres 16414.4 Clinical Signs of Lesions in Extrapyramidal Motor Centres in Man 16514.5 Clinical Signs of Lesions in the Basal Nuclei in Domestic Animals 16614.6 Upper Motor Neuron Disorders 16615 Summary of the Somatic Motor Systems 169The Motor Components of the Neuraxis 16915.1 Pyramidal System 16915.2 Extrapyramidal System 17015.3 Distinction between Pyramidal and Extrapyramidal Systems 171Clinical Signs of Motor System Injuries 17115.4 Functions of the Pyramidal and Extrapyramidal Systems: Effects of Injury to the Motor Command Centres 17115.5 Upper Motor Neuron 17115.6 Lower Motor Neuron 17215.7 Summary of Projections onto the Final Common Path 17316 The Cerebellum 175Afferent Pathways to the Cerebellum 17516.1 Ascending from the Spinal Cord 17516.2 Feedback Input into the Cerebellar Cortex 175Arterial Supply to the Brain 177Summary of Pathways in the Cerebellar Peduncles 17816.3 Caudal Cerebellar Peduncle 17916.4 Middle Cerebellar Peduncle 17916.5 Rostral Cerebellar Peduncle 179Rostral Cerebellar Peduncle 17916.6 Vestibular Areas 17916.7 Proprioceptive Areas 17916.8 Feedback Areas 180Functions of the Cerebellum 18016.9 Co‐ordination and Regulation of Movement 18016.10 Control of Posture 18116.11 Ipsilateral Function of the Cerebellum 18116.12 Summary of Cerebellar Function 18116.13 Functional Histology of the Cerebellum 182Clinical Conditions of the Cerebellum 18416.14 The Three Cerebellar Syndromes 18416.15 Cerebellar Disease in Domestic Mammals and Man 18517 Autonomic Components of the Central Nervous System 187Neocortex and Hippocampus 18717.1 Cortical Components 18717.2 Hippocampus 188Diencephalon 18817.3 Hypothalamus 188The Autonomic Functions of the Hypothalamus 19017.4 Amygdaloid Body and Septal Nuclei 19217.5 Habenular Nuclei 19317.6 Hindbrain Autonomic Areas 193The Autonomic Areas of the Hindbrain 19317.7 Autonomic Motor Pathways in the Spinal Cord 19417.8 Ascending (Afferent) Visceral Pathways in the Spinal Cord and Brainstem 195Clinical Disorders of the Autonomic System 19517.9 Effects of Lesions in Autonomic Pathways 19517.10 Summary of Descending Autonomic Pathways 19718 The Cerebral Cortex and Thalamus 199Cerebral Cortex 19918.1 Projection Areas and Association Areas 19918.2 Instinct 20018.3 Cerebral Cortex in Primitive Mammals 20018.4 Cerebral Cortex in the Cat and Dog 20018.5 Conditioned Reflexes 20018.6 Cerebral Cortex in Man 20118.7 Cognitive Association Area in Man 20218.8 Cognitive Association Area in Carnivores 20318.9 Interpretative Association Area in Man 20418.10 Interpretative Association Area in Carnivores 20418.11 Frontal Association Area in Man 20418.12 Frontal Association Area in Carnivores 20518.13 Corpus Callosum 205Clinical Conditions of the Cerebral Cortex 20518.14 Effects of Extensive Damage to the Cerebral Hemisphere in Domestic Mammals 20518.15 Seizures 207Histology of the Cerebral Cortex 20818.16 Histology of the Cerebral Cortex 208Thalamus 20818.17 Ventral Group of Thalamic Nuclei 20918.18 The Lateral Group 21018.19 Central (or Intralaminar) Group 21018.20 Dorsomedial Group 21018.21 Summary of Incoming Afferent Paths to the Thalamus: 21018.22 Summary of the Projections from the Thalamus to the Cerebral Cortex 21118.23 Summary of Functions of the Thalamus: 21118.24 Clinical Effects of Lesions of the Thalamus in Domestic Mammals 21218.25 Clinical Effects of Lesions of the Thalamus in Man 212Growth of the Human Brain 21219 Embryological and Comparative Neuroanatomy 215The Embryological Development of the Central Nervous System 21519.1 The Development of the Brain 21519.2 The Development of the Spinal Cord 21719.3 The Development of the Neural Crest 217Evolution of the Vertebrate Forebrain 21819.4 Primitive Vertebrates 21819.5 Contemporary Amphibian 21819.6 Contemporary Advanced Reptile 21919.7 Mammal 22019.8 Bird 22119.9 Major Homologies in Mammals and Birds 222Evolution of the Capacity to Differentiate Sensory Modalities 22319.10 Lower Vertebrates, Including Amphibians 22319.11 Advanced Reptiles and Birds 22319.12 Mammals 223Special Features of the Avian Brain 22319.13 Size of the Brain 22319.14 Poor Development of the Cerebral Cortex 22319.15 External Striatum 22419.16 Colliculi: The Optic Lobe 22419.17 Olfactory Areas 22419.18 Cerebellum 22519.19 Spinocerebellar Pathways 22619.20 Cuneate and Gracile Fascicles 22619.21 Motor Spinal Pathways 22720 Clinical Neurology 22920.1 Mental Status 22920.2 Posture 23020.3 Gait 23020.4 Examination of the Cranial Nerves: Tests and Observations 232Testing Postural and Locomotor Responses 24320.5 Tonic Neck and Eye Responses 24320.6 Proprioceptive Positioning Responses 24320.7 Placing Responses 24420.8 Extensor Postural Thrust 24520.9 Hopping 24520.10 Wheelbarrow Test 24520.11 Hemiwalking 24620.12 Righting 24720.13 Blindfolding 24720.14 Circling Test 24720.15 Sway Test 247Examination of Spinal Reflexes 24720.16 Withdrawal (Flexor) Reflex 24720.17 Patellar Tendon Reflex 24920.18 Triceps Tendon Reflex 25020.19 Biceps Tendon Reflex 25020.20 Cutaneous Trunci/Colli (Formerly Panniculus) Reflex 25020.21 Perineal Reflex 25120.22 Crossed Extensor Reflex 25120.23 Babinski Reflex 251Other Tests 25220.24 Assessment of Muscle Tone 25220.25 Testing Conscious Pain Responses 25220.26 Detecting Discomfort 25220.27 Testing the Sympathetic System 25220.28 Case Sheet 25421 Imaging Techniques for Study of the Central Nervous System 257General Considerations 25721.1 Species 25721.2 Objectives of Imaging in Clinical Neurology 25721.3 Computed Tomography and Magnetic Resonance Imaging 25821.4 The Use of Contrast Agents in Imaging 260Intracranial Structures 26221.5 Positioning of the Head 26221.6 Breed and Age Variation in Images of the Head 262Vertebral Column 26321.7 Positioning of the Patient 26321.8 Imaging the Vertebral Column 26421.9 Contrast Radiography of the Vertebral Column 26722 Topographical Anatomy of the Central Nervous System 269Spinal Cord 26922.1 Regions of the Spinal Cord 26922.2 Segments of Spinal Cord and their Relationship to Vertebrae 27022.3 General Organisation of Grey and White Matter 27022.4 Dorsal, Lateral and Ventral Horns of Grey Matter 27122.5 Laminae of Grey Matter 27222.6 Funiculi of White Matter 27222.7 Tracts of the White Matter 273Medulla Oblongata 27422.8 Gross Structure 27422.9 Cranial Nerves 27422.10 Ventricular System 27522.11 Internal Structure 277Pons 28022.12 Gross Structure 28022.13 Cranial Nerves 28022.14 Ventricular System 28122.15 Internal Structure 281Midbrain 28322.16 Gross Structure 28322.17 Cranial Nerves 28322.18 Ventricular System 28422.19 Internal Structure 284Diencephalon 28822.20 Gross Structure 28822.21 Cranial Nerves 28922.22 Ventricular System 28922.23 Internal Structure 290Cerebellum 29322.24 Gross Structure 29322.25 Internal Structure 29322.26 Cerebellar Peduncles 294Cerebral Hemispheres 29522.27 Gross Structure 29522.28 Ventricular System 29622.29 Internal Structure 29723 Electrodiagnostics 30323.1 Introduction 30323.2 Electromyography 30323.3 Nerve Conduction Velocity 30423.4 Electroencephalography 30423.5 Evoked Potentials 30523.6 Electroretinography 30723.7 Intra‐operative Monitoring of Spinal Cord Function 30724 Diagnostic Exercises 30924.1 Introduction 30924.2 Solutions to Diagnostic Exercises 317Appendix 325Further Reading 335Index 347