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Chapter 51 Disorders of Brain Function

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1 Chapter 51 Disorders of Brain Function

2 Conditions Causing Injury to the Brain
Trauma Tumors Stroke Metabolic derangements Degenerative disorders

3 Common Pathways of Brain Damage
The effects of ischemia Excitatory amino acid injury Cerebral edema Injury due to increased intracranial pressure (ICP)

4 Hypoxia and Ischemia Hypoxia
A deprivation of oxygen with maintained blood flow Ischemia Reduced or interrupted blood flow Focal cerebral ischemia: stroke Global cerebral ischemia: myocardial infarction

5 The large hemorrhage in this adult brain arose in the basal ganglia region of a patient with hypertension. This is one cause for a "stroke".

6 A blood clot is seen over the external surface of the dura
A blood clot is seen over the external surface of the dura. Thus, this is an epidural hematoma. Such a location for hemorrhage is virtually always the result of trauma that causes a tear in the middle meningeal artery.

7 Injury From Excitatory Amino Acids
Definition Injury to neurons caused by overstimulation of receptors for specific amino acids that act as excitatory neurotransmitters Causes Stroke Hypoglycemic injury Trauma to chronic degenerative disorders such as Huntington disease and Alzheimer dementia

8 The cerebral arterial circulation at the base of the brain is diagrammed here. A berry aneurysm is diagrammed at the final bifurcation of the right internal carotid artery. The most common locations for berry aneurysms are in the region of the anterior communicating and anterior cerebral, at the trifurcation of the middle cerebral, and at the bifurcation of internal carotid with posterior communicating. Vertebral-basilar aneurysms comprise <10% of cases. Multiple aneurysms occur in about 20 to 30% of cases.

9 The white arrow on the black card marks the site of a ruptured berry aneurysm in the circle of Willis. This is a major cause for subarachnoid hemorrhage.

10 The circle of Willis has been dissected, and three berry aneurysms are seen. Multiple aneurysms are seen in about 20-30% of cases of berry aneurysm. Such aneurysms are "congenital" in the sense that the defect in the arterial wall is present from birth, but the actual aneurysm takes years to develop, so that rupture is most likely to occur in young to middle age adults.

11 The subarachnoid hemorrhage from a ruptured aneurysm is more of an irritant producing vasospasm than a mass lesion.

12 Another cause for hemorrhage, particularly in persons aged 10 to 30, is a vascular malformation. Seen here is a mass of irregular, tortuous vessels over the left posterior parietal region.

13 The intraventricular and intracerebral hemorrhage seen here was due to a ruptured vascular malformation. The hemorrhage from such a lesion (which is most often histologically an arteriovenous malformation--AVM) can be intracerebral or extend into ventricles or subarachnoid space.

14 The characteristic location of the hemorrhage in this brain is consistent with a fall backwards resulting in a contrecoup injury to the inferior frontal and temporal lobes. This has resulted in extensive contusions and subarachnoid hemorrhage.

15 Question Which of the following is not a common cause of neural injury? Recreational drug use Ischemia Excitatory amino acids Cerebral edema Increased intracranial pressure (ICP)

16 Answer Recreational drug use: Drug use can cause damage, but it is not a common cause. Ischemia Excitatory amino acids Cerebral edema Increased intracranial pressure (ICP)

17 Intracranial Pressure
Increased ICP is a common pathway for brain injury. Obstruction of cerebral blood flow, destruction of brain cells, displacement of brain tissue, and damage to delicate brain structures Cranial cavity 10% blood, 80% brain tissue, 10% CSF Normal ICP 0–15 mm Hg

18 Brain Herniation Cingulate Involves cerebral artery
Clinical sign: leg weakness Central transtentorial Involves reticular activating system and corticospinal tract Clinical signs: altered level of consciousness, decorticate posturing, rostral-caudal deterioration

19 Brain Herniation (cont.)
Uncal Involves cerebral peduncle, oculomotor nerve, posterior cerebral artery, cerebellar tonsil, respiratory center Clinical signs: hemiparesis, pupil dilation, visual field loss, respiratory arrest

20 Hydrocephalus Definition
An abnormal increase in CSF volume in any part or all of the ventricular system Enlargement of the CSF compartment occurs Types Communicating Decreased absorption of CSF Noncommunicating Overproduction of CSF

21 Cerebral Edema Vasogenic edema
Occurs with conditions that impair the function of the blood-brain barrier and that allow transfer of water and protein from the vascular into the interstitial space Cytotoxic edema Involves an increase in intracellular fluid Interstitial cerebral edema Edema of the central white matter, as in hydrocephalus, affecting the brain

22 Classifications of Skull Fractures
Simple or linear A break in the continuity of bone Comminuted A splintered or multiple fracture line Depressed Bone fragments are embedded into the brain tissue Basilar A fracture of the bones that form the base of the skull

23 Types of Brain Injuries
Primary or direct injuries Damage is caused by impact. Include diffuse axonal injury and the focal lesions of laceration, contusion, and hemorrhage Secondary injuries Damage results from the subsequent brain swelling, infection, cerebral hypoxia Often diffuse or multifocal, including concussion, infection, and hypoxic brain injury

24 A coronal section through the frontal lobes reveals extensive contusions involving the inferior gyri. This was a contrecoup injury from a fall in the bathtub by an elderly person.

25 Coup–Contrecoup The brain floats freely in the CSF. Blunt force to the head accelerates the brain within the skull, and then the brain decelerates abruptly upon hitting the inner skull surfaces. Coup: direct contusion of the brain at the site of external force Contrecoup: rebound injury on the opposite side of the brain

26 The orange-brown, scalloped appearance of these lesions is consistent with old contusions. The resolution left behind hemosiderin from the hemorrhage that produces the orange-brown staining.

27 Seen here are remote contusions, mainly of the right inferior frontal lobe. The crests of the gyri are most susceptible to the traumatic forces.

28 Postconcussion Syndrome
Concussion refers to an immediate and transient loss of consciousness accompanied by a brief period of amnesia after a blow to the head. Recovery usually takes place in 24 hours. Mild symptoms may persist for months. Headache Irritability Insomnia Poor concentration and memory

29 Types of Hematomas Epidural hematoma
Usually caused by head injury in which the skull is fractured Develops between the inner table of the bones of the skull and the dura Subdural hematoma Usually is the result of a tear in the small bridging veins that connect veins on the surface of the cortex to dural sinuses Develops in the area between the dura and the arachnoid (subdural space)

30 The dura has been reflected back (with a small portion visible at the lower right) to reveal a subdural hematoma. Such a blood clot is usually the result of trauma with tearing of the bridging veins.

31 Hemorrhages involving the basal ganglia area (the putamen in particular) tend to be non-traumatic and caused by hypertension, which damages and weakens the small penetrating arteries. A mass effect with midline shift, often with secondary edema, may lead to herniation.

32 The dura has been reflected above to reveal the bridging veins that extend across to the superior aspect of the cerebral hemispheres. These can be torn with trauma, particularly if there is significant cerebral atrophy that exposes these veins even more.

33 Here is a bilateral chronic subdural hematoma
Here is a bilateral chronic subdural hematoma. The blood clots are brown to tan because of organization. Since the bleeding is venous, subdurals can form more slowly and insidiously than clots from arterial hemorrhages. Subdurals are most common in the very young and the elderly.

34 Types of Hematomas (cont.)
Traumatic intracerebral hematoma May be single or multiple Occurs in any lobe of the brain but is most common in the frontal or temporal lobes

35 Question Rotational acceleration of the head may result in which type of injury? Coup Contrecoup

36 Answer Coup Contrecoup: Contrecoup injury is rebound injury on the opposite side of the brain.

37 Manifestations of Global Brain Injury
Alterations in sensory and motor function Changes in the level of consciousness Rostral-to-caudal stepwise progression As the diencephalon, midbrain, pons, and medulla are affected, additional respiratory, pupillary and eye movement reflexes, and motor signs become evident.

38 Levels of Consciousness
Confusion Delirium Obtundation Stupor Coma

39 Signs of Diminution in Level of Consciousness
Earliest signs Inattention, mild confusion, disorientation, and blunted responsiveness With further deterioration The person becomes markedly inattentive and variably lethargic or agitated. The person may progress to become obtunded and may respond only to vigorous or noxious stimuli.

40 Medical Documentation of Brain Death
Cause and irreversibility of the condition Absence of brain stem reflexes and motor responses to pain Absence of respiration with a PCO2 of 60 mm Hg or more The justification for use of confirmatory tests and their results

41 Criteria for Diagnosis of Vegetative State
Absence of awareness of self and environment An inability to interact with others Absence of sustained or reproducible voluntary behavioral responses Lack of language comprehension Hypothalamic and brain stem function to maintain life

42 Criteria for Diagnosis of Vegetative State
Bowel and bladder incontinence Variably preserved cranial nerve and spinal cord reflexes Condition has continued for at least 1 month

43 Structures Supplying Blood Flow to the Brain
Two internal carotid arteries anteriorly Ophthalmic, posterior communicating, anterior choroidal, anterior cerebral, and middle cerebral Vertebral arteries posteriorly Internal carotid and vertebral arteries communicate at the base of the brain through the circle of Willis.

44 Cerebral Blood Flow Autoregulation Sympathetic stimulation
Metabolic factors Carbon dioxide Hydrogen ion Oxygen concentration

45 Two Main Types of Strokes (Brain Attack)
Ischemic strokes Caused by an interruption of blood flow in a cerebral vessel and are the most common type of stroke, accounting for 70–80% of all strokes. Hemorrhagic strokes Caused by bleeding into brain tissue, usually from a blood vessel rupture caused by hypertension, aneurysms, arteriovenous malformations, head injury, or blood dyscrasias

46 Warning Signs and Danger Zones
Ischemic penumbra in evolving stroke Transient ischemic stroke Brain angina Watershed zone

47 Signs and Symptoms of Cerebral Aneurysms
Most small aneurysms are asymptomatic. Large aneurysms may cause chronic headache, neurologic deficits, or both. Other manifestations include signs of meningeal irritation, cranial nerve deficits, stroke syndrome, cerebral edema and increased ICP, and pituitary dysfunction. Hypertension and cardiac dysrhythmias result from massive release of catecholamines triggered by the subarachnoid hemorrhage.

48 Aneurysmal Subarachnoid Hemorrhage
Bleeding into the subarachnoid space Causes Congenital defect Acute increases in ICP Cigarette smoking Hypertension Excessive alcohol intake

49 Hemodynamic Effects of Arteriovenous Malformations
First, blood is shunted from the high-pressure arterial system to the low-pressure venous system without the buffering advantage of the capillary network. The draining venous channels are exposed to high levels of pressure, predisposing them to rupture and hemorrhage. Second, the elevated arterial and venous pressures divert blood away from the surrounding tissue, impairing tissue perfusion.

50 Risk Factors and Deficits of Stroke
Age, sex, race Family history Hypertension Smoking Diabetes mellitus Asymptomatic carotid stenosis Sickle cell disease Hyperlipidemia Atrial fibrillation Stroke-related deficits Motor deficits Dysarthria and aphasia Cognitive and other deficits

51 Classifications of Infections of the CNS
By structure Meninges: meningitis Brain parenchyma: encephalitis Spinal cord, myelitis Brain and spinal cord: encephalomyelitis By type of invading organism Bacterial, viral, or other

52 Meningitis Inflammation of the pia mater, the arachnoid, and the CSF-filled subarachnoid space Fever and chills, headache, stiff neck, back, abdominal, and extremity pains, nausea and vomiting Acute lymphocytic meningitis Acute purulent meningitis Bacterial meningitis Pneumococcus Meningococcus Viral meningitis

53 Encephalitis Types Viral
Herpes simplex virus, West Nile virus Bacterial Fungal Infection of the parenchyma of the brain or spinal cord Local necrotizing hemorrhage Progressive degeneration of nerve cell bodies Prominent edema Transmission Ingestion Mosquito Rabid animal

54 Classification of Brain Tumors
Primary intracranial tumors of neuroepithelial tissue Neurons, neuroglia Primary intracranial tumors that originate in the skull cavity but are not derived from the brain tissue itself Meninges, pituitary gland, pineal gland, primary CNS lymphoma Metastatic tumors Benign vs. malignant

55 Types and Symptoms of Brain Tumors
Ependymomas Meningiomas Primary CNS lymphomas Increased ICP Focal disturbances in brain function Edema Disturbances in blood flow Tumor infiltration Brain compression

56 Treatment and Evaluation Methods for Brain Tumors
MRI CT scans Electroencephalogram Visual field and funduscopic examination Include physical and neurologic examinations Surgery Irradiation Chemotherapy

57 Seizures and Convulsions
Abnormal behavior caused by an electrical discharge from neurons in the cerebral cortex A discrete clinical event with associated signs and symptoms which vary according to the site of neuronal discharge in the brain Manifestations generally include sensory, motor, autonomic, or psychic phenomena. Convulsion Specific seizure type of a motor seizure involving the entire body

58 Epilepsy Syndromes of associated seizure types EEG patterns
Exam findings Hereditary patterns Precipitating factors

59 Types of Seizures Partial seizures Simple partial seizures
Complex partial seizures Partial seizures evolving to secondarily generalized seizures Unclassified seizures Inadequate or incomplete data

60 Types of Seizures Generalized seizures Absence seizures
Atonic seizures Myclonic seizures Tonic seizures Tonic-clonic seizures

61 Status Epilepticus Continual seizures Do not stop spontaneously
Many types If untreated or not stopped can lead to death due to respiratory failure

62 Question Which type of stroke is the result of a ruptured blood vessel? Ischemic TIA Arteriovenous malformation Hemorrhagic

63 Answer Ischemic TIA Arteriovenous malformation
Hemorrhagic: These strokes are caused by the rupturing of a major vessel in the brain.

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