Clinical Connections

1. Clinical Connections

2. Clinical Connection: Spina Bifida • Defective closure of the caudal neural tube • Variabilility in severity • Spina bifida oculta • Spina bifida cystica • Spina bifida with myelomeningocele • Spina bifida with meningomyelocele • Spina bifida with myeloschisis

3. Clinical Connection: Spina Bifida • Often occurs with other congenital anomalies • Incidence declining with early prenatal detection and dietary supplement of folic acid

4. Image spina bifida

5. Clinical Connection: Arnold-Chiari Malformation • Associated often with spina bifida with meningomyelocele • Congenital anomaly • Medulla and posterior cerebellum elongate into foramen magnum • May be asymptomatic • May result in hydrocephalus and other symptoms

6. Clinical Connection: Anencephaly • Congenital anomaly • Failure of rostral neuropore closure • Large portions of scalp, cranial bones, and cerebral hemispheres are absent • Most die in utero, virtually all by first postnatal week

7. Clinical Application Exercise • Discuss the stories of Maria Rodriquez and Jonathan Perry • Mechanism of injury • For Maria, do you predict motor loss, sensory loss or both? Why? Both, Ant/post • Predict her ‘motor picture’ mid trunk & up • Will she walk? No • For Jonathan, which part of the cord has the tumor affected? Posterior

8. Clinical Connection: Nervous System Pathology • Retrograde transport of certain toxins and viruses from the environment to the CNS • Examples • Clostridium tetani bacterium • Rabies • Herpes simplex virus • Poliomyelitis

9. Clinical Connection: Multiple Sclerosis • Autoimmune disorder • Proteins expressed by oligodendrocytes are erroneously recognized as foreign by immune system • Loss of myelin in brain and spinal cord

10. Clinical Connection:Parkinson's Disease (PD) • In PD there is a degeneration of dopamine (DA) producing cells and a substantial reduction in the synthesis of DA • Most common treatment strategy is replacement therapy of DA

11. Clinical Connection:Parkinson's Disease (PD) • DA cannot cross blood–brain barrier, but precursor L-DOPA does • L-DOPA stimulates surviving DA cells to increase synthesis of DA

12. Clinical Connection:Biologic Depression • May be due to a deficiency in brain of amine transmitters – norepinephrine (NE) and serotonin (5-HT) • Monoamine oxidase is an enzyme that breaks done NE and 5-HT • Treatment historically included MAO inhibitors • MAO inhibitors have unwanted side effects

13. Clinical Connection: Syndrome of the Anterior Spinal Artery • Usually acute onset due to ischemia of lower thoracic or upper lumbar spinal cord

14. Clinical Connection: Syndrome of the Anterior Spinal Artery • Characterized initially by • Flaccid paraplegia in both legs • Bilateral deficits in STT sensibilities • Loss of bowel and bladder control • Sparing of DCML sensibilities • Following spinal shock, spastic paraplegia may develop

15. Clinical Connection: Herniation of the Vertebral Disc • Displacement of disc tissue from normal position between vertebral bodies • Nuclear protrusion mild • Disc prolapse more severe

16. Disc Herniations

17. Clinical Connection: Herniation of the Vertebral Disc • May compress the spinal cord against the vertebral canal of the spinal nerves against the intervertebral foramina • Most herniations are in a posterolateral direction • Common levels for herniations correspond to areas where vertebral column moves freest • L5/S1, C5/C6, C6/C7

18. Clinical Connection: Vertebral Fractures and Neurotoxic Spinal Cord Injury • With vertebral dislocations or fracture dislocations the spinal cord can be damaged immediately by trauma or subsequently through secondary neurochemical injury • Endogenous neurotransmitters cause excitotoxic neuronal cell death • Initial trauma causes changes in ions leading to cytotoxic edema

19. Clinical Connection: Cervical Spondylosis • Degeneration of the discs and surrounding ligaments, osteophytic changes • Lower cervical vertebra particularly vulnerable

20. Clinical Connection: Cervical Spondylosis • Results in compression and compromised blood supply of spinal cord • Characterized by neck pain and stiffness, hand numbness, and spastic leg weakness

21. Spondylosis

22. Clinical Connection: Control of the Level of Consciousness • The portion of the RF that contributes to the level of consciousness is called the ascending reticular activating system (ARAS) • Sleep is a part of this, epithalamus is main contributor of cycles (melatonin)

23. Clinical Connection: Control of the Level of Consciousness • Levels of consciousness • Attention • Alertness • Drowsiness • Stupor • Coma

24. Clinical Connection: Thalamic Syndrome • Typically caused by occlusion of thalamogeniculate branches of the PCA supplying posterior thalamus • Symptoms contralateral to lesion • Hemianesthesia, ataxia, excruciating neurogenic pain Symptoms in diff proportions in diff pts • Unresponsive to analgesics

25. Clinical Connection: Hypothalamic Syndromes • Diabetes INSIPIDUS • Problems with regulation of thirst, hunger, and body temperature; menstrual and sleep–wakefulness cycles

26. Clinical Connection:Cerebellar Dysfunction • Variety of causes • Acute/chronic alcohol intoxication, developmental disorders, stroke, trauma • Characteristic symptoms • Hypotonia, incoordination, intention tremor, ataxia, nystagmus

27. Clinical Connection: Involuntary Movements Attributed to Basal Ganglia Dysfunction • Tremor-rhythmic, alternating movement of a body part • Athetosis – slow, sinuous, writhing movements • Chorea – brisk, graceful, complex movements (caudate) • Ballismus – forceful, flinging movements (subthalamic)

28. Clinical Connection: Occlusion of the MCA • Occlusion of the superior division of the MCA • Structures affected: BAs 4, 3, 1, 2, 8, 44, 45 • Related symptoms include contralateral motor and sensory deficits, eye movement deficits, and motor aphasia if dominant hemisphere occluded • Problem with language production

29. Clinical Connection: Occlusion of the MCA • Occlusion of the inferior division of the MCA • Structures affected: BAs 22, 39, 40 • Related symptoms include sensory aphasia if dominant hemisphere occluded, visuospatial deficits if nondominant hemisphere occluded

30. Figure 7-20 (a) Area of the left cerebral hemisphere infarcted by occlusion of the left superior division of the MCA. Note that the damage is confined to the frontal lobe and postcentral gyrus of the parietal lobe. (b) Area of the left hemisphere infarcted by occlusion of the inferior division of the MCA. Note that the damage is confined to the posterior portion of the parietal lobe and the temporal lobe. Abbreviation: BA, Brodmann's area. (Adapted from Bowman, J. P., and Giddings, D. F. Strokes: An Illustrated Guide to Brain Structure, Blood Supply, and Clinical Signs. Prentice Hall,New Jersey, 2003.)

31. Clinical Connection: Occlusion of the ACA • Less common than occlusion of the MCA or IC • Structures damaged include the medial aspects of BA 4, 3, 1, 2 • Related symptoms include contralateral motor and sensory deficits that are most severe in the lower extremity

32. Occlusion of the ACA

33. Clinical Connection: Occlusion of the IC • Carotid border syndrome occurs with occlusion of 70% or more of the IC • Blood flow to the distal territories is decreased, but not eliminated • Symptoms include contralateral numbness and weakness

34. Clinical Connection: Occlusion of the PCA • Structures affected include BA 17, the primary visual cortex • Related symptoms include loss of vision in the contralateral one-half of the visual field of each eye • Because a branch of MCA perfuses the cortex that receives afferents from the fovea, there may be sparing of foveal vision (macular sparing)

35. Clinical Connection: Motor Signs • Positive signs (release phenomena) • An excess of neural activity • Hyperreflexia, hypertonicity, Babinski sign • Negative signs • Motor deficits due to the loss of function of damaged neural structures • Weakness, loss of speed of movement, loss of dexterity

36. Clinical Connections • Peripheral neuropathies typically impair somatosensation and autonomic functions • Herpes zoster (shingles) is a viral infection of the somatosensory ganglia of the peripheral and cranial nerves (ophthalamic

37. Clinical Connections: Disorders of Peripheral Nerves • Neuropathy – disease of the peripheral nerves • Mononeuropathy – affecting one nerve • Polyneuropathy – affecting many nerves • Radiculopathy – affecting spinal nerve roots

38. Clinical Connections: Disorders of Peripheral Nerves • Diabetes mellitus (DM) is the most common cause of polyneuropathy • Characterized by distal, bilateral sensory losses

39. Clinical Connection: Brown-Sequard Syndrome • Lesion of one-half of the spinal cord and all fibers entering the cord via the dorsal root producing • Ipsilateral zone of somatosensory anesthesia at the damaged dermatomes • Ipsilateral loss of DC-ML modalities below the lesion • Contralateral loss of STT modalities below the lesion

40. Clinical Connection: Syringomyelia • Disease process in the center of the spinal cord, usually over a few cervical segments • Disrupts pain and temperature fibers of the STT in the ventral white commissure • Characterized by bilateral loss or pain and temperature sensibility, usually in the hands and arms

41. Clinical Connection: Subacute Combined Degeneration • Disorder that typically first involves the fibers of the dorsal columns • Related to lack of Vitamin B12 absorption • Early symptoms include symmetrical parathesias of fingers and toes and loss of proprioception • Person may demonstrate unsteady, ataxic gait

42. Clinical Connection: LMN Syndrome • Damage to the LMN cell body or axon • Characterized by: • Hyporeflexia • Hypotonia • Paralysis (loss) or paresis (weakness) • Atrophy = rapid and severe • Denervation • Fasciculations = can happen in tired, healthy people or LMN damage = visible twitch • Fibrillations = similar to fasciculation, smaller, need EMG, not visible twitch

43. Clinical Connection: Diseases of the Motor Unit • Four sites of the motor unit can be attacked by specific disease entities • The cell body of the LMN, its axon, the neuromuscular junction, or the muscle fibers • Neurogenic-affecting cell body or axons • (e.g., polio, neuropathies) • Myopathic-affecting striated muscle • (e.g., myasthenia gravis)

44. Clinical Connection: Polio • Viral infection, prevented by vaccination • Attacks cell bodies of LMNs • Cardinal clinical signs: weakness/paralysis, atrophy, and decreased reflexes • Postpolio syndrome may appear 20–30 years after the acute infection • Remaining neurons overworked after normal neuron apoptosis

45. Clinical Connection: Neuropathies • Pathological changes of the peripheral nerves • Segmental degeneration • Axonal degeneration • Wallerian degeneration • Diabetes mellitus (DM) • Acute inflammatory demyelinatingpolyneuropathy (AIDP) = aka guillannebarre’s

46. Clinical Connection: Myasthenia Gravis • Autoimmune disorder of neuromuscular transmission resulting in weakness • Typically eye muscles are affected first, resulting in ptosis and diplopia • Muscles of facial expression, mastication, swallowing, and speech are typically affected next, resulting in altered facial expression, dysphagia, and dysarthria

47. Clinical Connection: Myopathies • Progressive hereditary diseases of skeletal muscle • Duchenne muscular dystrophy • Defective gene that codes for protein dystrophin • Sex-linked recessive trait transmitted from mother to male children

48. Clinical Connection: Myopathies • Duchenne muscular dystrophy • Lack of dystrophin renders sarcolemma vulnerable • Weakness, tearing, and loss of muscle fibers • Shortens life expectancy to late adolescence or early adulthood

49. Duchenne Muscular Dystrophy

50. Clinical Connection: Amyotrophic Lateral Sclerosis • Also called Lou Gehrig's disease • Most frequent motor system disease • Characterized by • amyotrophy (weakness, denervation, atrophy) • lateral sclerosis (upper motor neuron signs)