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NEUROANATOMY

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NEUROANATOMY NEUROANATOMY Presentation Transcript

  • NEUROANATOMY (Related to Stroke) Dubbo Stroke Forum 21st November 2007 Presented by: Sharon Eriksson CNC Stroke POWH
  • Overview Overview of the Nervous system Functions of the Nervous system Neuroanatomy (including) - Functional Areas of the brain - Cerebro Spinal Fluid - Cranial nerves - Cerebral Circulation
  • ANATOMY Central Nervous System Brain Spinal Cord Peripheral Nervous System Cranial Nerves Spinal Nerves Autonomic Nervous System Sympathetic Parasympathetic
  • Functions of the Nervous System Control and communication system Monitors Changes inside and outside the body (sensory input) Processes and interprets sensory input and makes decisions (integration) Affects a response (motor output) by affecting glands, muscles etc. Works closely in conjunction with the endocrine system
  • Nerve Transmission Neurons - Basic anatomic and functional unit of the nervous system Respond to sensory and chemical stimuli, conduct impulses and release specific chemical regulators A nerve impulse is a wave of electrical charge sweeping from neuron to neuron The gap lying between one neuron and the next is the synapse Neurotransmitters move across the synapse where they excite, inhibit or modify
  • Neuro Anatomy 3 structures serve to protect the brain 1. Scalp 2. Skull 3. Meninges SKULL 22 bones in total • 8 make up the cranium, other 14 facial bones • Cranium is that part of the skull that encloses the brain (cranial vault)
  • SKULL
  • Monro-Kellie Hypothesis The skull is a rigid box (once the sutures have fused) 3 components within that have a balance - 80% brain - 10% blood - 10% CSF If any one of these components increase4s another must decrease to maintain the balance (ICP) If this does not happen then there will be an increase in ICP
  • Meninges • 3 layers that lay directly on the surface of the brain tissue (parenchyma) and spinal cord. Offer a cushioning effect. • Dura Mater - outer most layer that is thick and fibrous, that lines the interior of the skull. • Arachnoid - middle layer, is extremely thin and loosely encloses the brain • Pia Mater - inner most, mesh like and very vascular. It follows the convolutions of the brain • Spaces of the meninges - extradural, subdural and subarachnoid
  • Meninges Dural Folds
  • Ventricular System • Produces (~ 500mL/day) and circulates (~ 150mL) CSF. • CSF is usually a clear colourless fluid that acts as a shock absorber • The ventricular system is connected to the subarachnoid space (SAS) • 3 main compartments - 2 lateral ventricles, 1 third ventricle and 1 fourth ventricle • CSF is produced by the choroid plexus in each ventricle • CSF is reabsorbed into the venous blood flow via the arachnoid villi • Arachnoid villi are small granulations that project from the SAS into the venous outlets of the brain.
  • Arachnoid Villi
  • The Brain (Encephalon) • Young adult male 1400gms – older people weigh less around 1200gms • Totally dependant on glucose for metabolism • Divided into three major areas 1. Cerebrum 2. Cerebellum 3. Brain stem CEREBRUM • The cerebrum is composed of 2 cerebral hemispheres, thalamus, hypothalamus and the basal ganglia (deep pockets of grey matter) • The hemispheres are connected by the corpus callosum
  • Lateral view Coronal view
  • CEREBRUM CONTINUED • Each hemisphere is covered by a cerebral cortex (grey matter) that is about 2 - 5 mm thick and contains billions of neurons • Under the cerebral cortex is the white matter which acts as the relay/projection system for the nerve pathways • Within the cortex (grey matter) are numerous different areas that control our functions • Brodman is credited with mapping the cortical areas of the brain
  • Brodman’s Cortical Mapping
  • Frontal Lobe General Functions • High level cognitive functions. i.e reasoning, abstraction, concentration • Storage of information – memory • Control of voluntary eye movement • Motor control of speech in the dominant hemisphere • Motor Cortex - Motor control of the contralateral side of the body • Urinary continence • Emotion and personality
  • Parietal Lobe General Functions • Sensory cortex – sensory input is interpreted to define size, weight, texture and consistency. (contralateral) • Sensation is localised, and modalities of touch, pressure and position are identified • Awareness of the parts of your body • Non-dominant – processes visuospatial information and controls spatial orientation • Dominant is involved in ideomotor praxis (ability to perform learned motor tasks)
  • Temporal Lobe General Functions • Primary auditory receptive areas • In dominant ability to comprehend speech (wernicke’s) – reception •Interpretive area – area at the junction of the temporal, parietal and occipital lobes. Plays an important role in visual, auditory and olfactory perception • Important role in learning; memory and emotional affect.
  • Occipital Lobe General Functions • Primary visual cortex • Visual association areas • Visual perception • Some visual reflexes (i.e. visual fixation) • Involuntary smooth eye movement
  • Coronal View of Motor and Sensory Cortex
  • Basal Ganglia • Several masses of sub-cortical nuclei (grey matter) located deep in the cerebral hemispheres. Lenticular nucleus, Caudate nucleus, Amygdaloid body and claustrum. • These structures control the motor control of fine body movements, particularly of the hands and lower extremities.
  • Diencephalon • Divided into 4 regions; Thalamus, hypothalamus, subthalamus and epithalamus • Internal capsule and hypophysis (pituitary gland) also located in this region • Thalamus – sensory relay centre. Plays a role in conscious pain awareness, in focusing of attention and the reticular activating system. • hypothalamus – regulates important physiological based drives such as appetite, sexual arousal and thirst. Controls; temperature, water metabolism (ADH), Pituitary secretions, sleep-wakefulness cycle. • Internal capsule is the area that the motor pathways from the cortex travel through
  • Cerebellum • Located in posterior fossa, it is attached to the brainstem • Its pathways are very complex • Its major functions are balance and coordination Brain Stem • Three major divisions - Midbrain - Pons - Medulla • 10 of the 12 pairs of cranial nerves arise from the brainstem (ipsilateral signs) • Cortical pathways pass through the brainstem and decussate (cross) in the medulla (contralateral signs) • Some of the major functions are: eye movement, swallowing, breathing, blood pressure, heat beat, consciousness
  • Brain Stem & Diencephalon
  • CEREBRAL CIRCULATION Vessels Feeding the Brain Anterior circulation from the carotid arteries Posterior circulation from the vertebral arteries
  • CEREBRO-VASCULAR CIRCULATION • 2 carotid arteries supply the anterior circulation The carotids bifurcate (split) into the Internal and exteral carotid IC Opth. A (C of W) MCA ACA ACOA • 2 vertebral arteries supply the posterior circulation VA PICA AICA BA SCA (C of W) PCA PCOA
  • CEREBRO-VASCULAR CIRCULATION
  • CEREBRO-VASCULAR CIRCULATION
  • INTERNAL CAROTID ARTERY • Not all ICA occlusions become symptomatic. It depends on the amount of collateral blood supply primarily from the C of W • The degree of deficits vary, from asymptomatic to a catastrophic infarction (similar to MCA)
  • MIDDLE CEREBRAL ARTERY • MCA is the largest branch that comes off the ICA • It has deep branches that supply part of the internal capsule and basal ganglia (putamen, caudate nucleus and globus pallidus) • It passes out to the lateral surface of the cerebral hemisphere where it supplies blood to the cortical areas of the temporal, frontal and parietal lobes
  • CLINICAL FEATURES OF MCA STROKE • Paralysis of the contralateral face, arm (more-so) and leg • Sensory impairment over the contralateral face, arm ( more-so) and leg • Homonymous hemi or quadrantonopia • Paralysis of gaze to the opposite side • Aphasia (dominant) and dysarthria • Unilateral neglect, apraxia and agnosia for half of external space (non-d) • Penetrating - contralateral hemiplegia/paresis, slurred speech
  • ANTERIOR CEREBRAL ARTERY • Runs above the optic nerve to follow the curve of the corpus callosum • The 2 ACA’s are connected by the ACOA • Deep (penetrating) branches of the ACA pass to the anterior part of the internal capsule and basal ganglia • Cortical branches supply the medial surface of the hemisphere (orbital, frontal parietal)
  • CLINICAL FEATURES OF ACA STROKE • Paralysis of contralateral foot and leg • Sensory loss over toes, foot and leg • Impairment of gait and stance • Abulia (slowness and prolonged delays to perform acts) • Flat affect, lack of spontaneity, slowness, distractibility • Cognitive impairment, such as perseveration and amnesia • Urinary incontinence
  • VERTEBRAL & BASILAR ARTERY • The VA and its branches supply the medulla and the inferior surface of the cerebellum • The BA supplies the brain stem from the medulla upwards and the posterior cerebellum. It divides into the 2 PCA. • Deficits to these territories could include – quadraplegia, Possibly the ‘locked in’syndrome, diplopia, ataxia, dizziness, vertigo, nystagmus, weakness of facial, lingual and pharyngeal muscles, dysarthria, dysphagia, unconsciousness
  • POSTERIOR CEREBRAL ARTERY • The terminal branches of the BA • Small perforating branches supply midbrain structures, choroid plexus and posterior thalamus • Cortical branches supply the under surface of the temporal lobe and the occipital lobe (visual cortex)
  • CLINICAL FEATURES OF PCA STROKE Peripheral (cortical) • Homonymous hemianopia • Memory deficits • Perseveration • Several visual deficits (cortical blindness, lack of depth perception, hallucinations) Central (penetrating) • Thalamus - contralateral sensory loss, spontaneous pain, mild hemi • Cerebral peduncle - CN III palsy with contralateral hemiplegia • Brain stem - CN palsies, nystagmus, pupillary abnormalities
  • Venous Drainage • Cerebral veins empty into dural sinuses which, in turn, empty into the jugular veins, which return the blood to the heart
  • Questions?
  • References Hankey, G.J. 2002. Stroke: Your Questions Answered. Churchill Livingstone; Sydney Hickey, J. 2003. The Clinical Practice of Neurological and Neurosurgical Nursing. 5th Ed. Lippincott; Philadelphia Hock, NH. 1999. Brain Attack. The Stroke Continuum. Nursing Clinics of North America. 34(3). 689-723 Goldszmidt, M.D & Caplan, L.R. 2003. Stroke Essentials. Physicians’ Press; Michigan Lindsay, K & Bone, I. 1999. Neurology and Neurosurgery Illustrated. 3rd Ed. Churchill Livingstone; London