Neuroanatomy and Intracranial Pressure Quiz

Neurologic Dysfunction

• This presentation covers neurologic dysfunction, specifically focusing on altered levels of consciousness.
• A fully conscious patient is aware of their surroundings. Levels of consciousness exist on a spectrum.

Levels of Consciousness

• Consciousness, Confusion, Somnolence, Obtundation, Stupor, Coma.
• Stupor and coma indicate advanced brain failure.

Altered Level of Consciousness

• Level of responsiveness and awareness is the key indicator of a patient's condition.
• Altered LOC is a result of a pathology, not the disorder itself.
• Various levels of altered consciousness are defined by specific responses to stimuli.

Coma, Persistent Vegetative State

• Coma is an unarousable, unresponsive state.
• There may be no purposeful responses to internal or external stimuli.
• However, some brain stem reflexes might be present.
• A persistent vegetative state is marked by sleep-wake cycles after a coma, but without cognitive or emotional function.

Glasgow Coma Scale

• The Glasgow Coma Scale (GCS) is a tool used to assess levels of coma.
• It evaluates eye opening, verbal response, and motor response.
• Each aspect is scored, with higher scores signifying better neurological function. A high GCS score corresponds to full consciousness

Assessment

• Verbal Response: Orientation to time, person, and place; degree of alertness. Responsiveness to sound stimuli.
• Alertness: The ability to open the eyes spontaneously or in response to stimuli.
• Motor Response: Purposeful movement in response to stimuli, movement in response to painful stimuli, or abnormal posturing.

Decorticate and Decerebrate Posturing

• Decorticate: characterized by flexion of upper extremities, internal rotation of the lower extremities and plantar flexion of the feet.
• Decerebrate: characterized by extension and outward rotation of the upper extremities and plantar flexion of the feet.

Respiratory Status

• In cases of serious deterioration, respirations can change from Cheyne-Stokes to a neurogenic hyperventilation pattern.
• The frequency of breaths can exceed 40 per minute.

Intracranial Pressure

• The cranial cavity contains blood, brain tissue, and cerebrospinal fluid (CSF).
• Normal ICP is maintained within a range from 5 to 15 mmHg.
• The Monro-Kellie doctrine states that intracranial volumes are constant.

Increased Intracranial Volume and Pressure

• The brain is enclosed in the rigid skull, making it vulnerable to increases in ICP.
• Excessive ICP can obstruct blood flow, displace brain tissue or damage delicate brain structures.
• Issues like brain tumors, edema (swelling), or bleeding can cause increases in ICP.

Major Causes of Increased ICP

• Intracranial mass lesions, such as tumors or hematomas.
• Cerebral edema due to severe brain injury.
• Increased CSF production (like in choroid plexus papilloma).
• Decreases in CSF absorption (like in arachnoid granulation adhesions).
• Obstruction of venous outflow (like in venous sinus thrombosis).

Compensatory Mechanisms

• Autoregulation: the brain adjusts blood vessel size to maintain constant blood flow.
• Initial compensation: displacement of blood, CSF, and the space-occupying lesion.
• Subsequent mechanisms include CSF displacement, blood vessel contraction, or drainage.

Compensatory Mechanisms (Continued)

• The brain attempts to accommodate increased volumes or pressures through different mechanisms to keep ICP normal. Mechanisms include displacements of CSF and blood, changes in blood vessel diameters; reducing brain swelling

Compensatory Mechanisms (Continued)

• If the increase in volume continues, the brain's adaptive mechanisms may become strained.
• Subsequently, ICP will rise beyond a safe range and may cause severe neurological consequences.

Cerebral Compliance and the Impact of ICP

• Cerebral compliance is the brain's capacity to change volume with minimal changes of pressure.
• The curve demonstrating intracranial volume changes on ICP shows that a small increase in volume corresponds to a higher increase in ICP

Volume-Pressure Relationship

• The intracranial volume-pressure curve demonstrates the relationship between intracranial volume and pressure.
• The volume curve shows that normal intracranial volume causes no change in ICP
• Small increases in intracranial volume, cause less change in ICP in early stages compared to large increases in intracranial volume.

Intracranial Pressure, ICP, and Cerebral Perfusion Pressure, CPP

• ICP and CPP (Cerebral perfusion pressure) are important variables in cerebral function; monitoring both factors is essential for proper patient care.
• Normal ICP range from 10 to 15mmHg and CPP range from 70 to 100

Impact of ICP on CPP

• MAP (mean arterial pressure) and ICP are frequently monitored.
• An increase in ICP can reduce perfusion pressure, potentially causing ischemia.
• Cerebral perfusion pressure (CPP) between 50 to 70 mmHg can cause ischemia.

Cellular Hypoxia and Neurological Deterioration

• Continued cellular hypoxia leads to progressive neurological deterioration.
• Level of consciousness may worsen from alertness to confusion, lethargy, obtundation, stupor, coma.
• Damage occurring for 3-10 minutes can be irreversible.

Increased PaCO2 and Cerebral Blood Flow

• Increased Carbon Dioxide (PaCO2) in the blood causes vasodilation resulting in higher cerebral blood flow, in turn, causing elevated ICP.
• Decreased PaCO2 conversely causes vasoconstriction and lower cerebral blood flow hence, decreasing ICP.

Cushing's Response

• Cushing's triad is a clinical phenomenon in which cerebral blood flow significantly declines.
• When ischemia happens, the vasomotor center increases arterial pressure to overcome elevated ICP, as well as widening of the pulse pressure and cardiac slowing.

Clinical Manifestations

• Signs such as headache, decreased LOC, vomiting, and papilledema can indicate increased ICP.
• The symptoms may reflect the location and severity of the pathology.

Cheyne-Stokes Respiration

• Cheyne-Stokes respiration is characterized by alternating periods of increased and decreased breathing depth.
• It is an abnormal respiratory pattern and a possible marker of elevated ICP and brain stem dysfunction.
• CNH is an abnormal respiratory pattern characterized by rapid, deep breaths, at an average rate of 25 per minute.
• The rapid breathing arises as a response to decreased CO2.

Respiratory Patterns

• Different patterns of breathing indicate specific problems in the central nervous system.
• These patterns can be observed when patients suffer from central nervous system diseases.

Brain Herniation

• Brain herniation occurs when increased intracranial pressure causes the brain tissue to shift from its normal position.
• Types include: Uncal, Central, Cingulate, Transcalvarial, Tectal, upward cerebellar and downward cerebellar. Different part of the brain displace

Management

• The primary management strategy for ICH is to address the causal issue directly;
• The most important immediate concerns are oxygenation, BP, and end-organ perfusion.
• Medical therapies like osmotic diuretics (mannitol), hypertonic saline, hyperventilation, positioning, sedation, and fever control are used to manage increased intracranial pressure.

Removal of CSF- Ventriculostomy

• External ventricular drains (EVDs) are small catheters often positioned to the lateral ventricle, for cerebrospinal fluid (CSF) drainage.
• EVDs are often used to record intracranial pressures.

Valsalva Maneuver

• Valsalva maneuver is characterized by increased intracranial pressure induced from sudden expulsion of blood from the thoracic vessels into the carotid vessels during bowel movement.
• It is essential to avoid increasing pressure in the cranial vault causing a subsequent increase in intracranial pressure.

Effect of High Temperature on ICP

• Fever is associated with elevated metabolic demand and raised cerebral blood flow that directly increases ICP.

Test your knowledge on the Glasgow Coma Scale and intracranial pressure dynamics with this quiz. Questions cover various aspects, including levels of consciousness, the Monro-Kellie hypothesis, and compensatory mechanisms of the brain. Ideal for students and professionals in neuroscience and medical fields.