Cranial Nerves Overview Quiz

Cranial Nerves

Olfactory Nerve (I): Responsible for the sense of smell. Dysfunction results in anosmia (absence of smell).
Optic Nerve (II): Responsible for vision. Dysfunction can cause blurring of vision or blindness.
Oculomotor Nerve (III): Controls eye movement and pupillary constriction. Damage can lead to anisocoria (unequal pupil).
Trochlear Nerve (IV): The smallest cranial nerve, controls eye movement.
Trigeminal Nerve (V): The largest cranial nerve. Responsible for sensation in the face, including pain and the oral cavity, corneal reflex, and chewing.
Abducens Nerve (VI): Controls eye movement.
Facial Nerve (VII): Controls facial expression, taste, and tears.
Vestibulocochlear Nerve (VIII): Responsible for hearing and balance. Dysfunction can cause hearing loss, tinnitus, or vertigo.
Glossopharyngeal Nerve (IX): Controls taste and swallowing.
Vagus Nerve (X): Controls the heart, lungs, and digestive system. Dysfunction can cause dysphagia (difficulty swallowing) and absence of the gag reflex.
Spinal Accessory Nerve (XI): Controls neck and shoulder movement.
Hypoglossal Nerve (XII): Controls tongue movement and speech. Dysfunction can cause tongue deviation and dysarthria (slurred or slow speech altering muscles for speech).

Level of Spinal Nerves

Cervical Nerves (C1-C8): Control diaphragm, chest wall muscles, shoulders, and arms.
Thoracic Nerves (T1-T12): Control upper body, including the digestive system.
Lumbar Nerves (L1-L5): Control the lower body.
Sacral Nerves (S1-S5): Control bowel and bladder function.
Coccygeal Nerve (Co1): The smallest spinal nerve, controls the tailbone.

Nervous System

Central Nervous System (CNS): Includes the brain and spinal cord.
Peripheral Nervous System (PNS): Includes cranial and spinal nerves.
Autonomic Nervous System (ANS): Controls involuntary bodily functions. It is further divided into the
- Sympathetic Nervous System: Responsible for the "fight-or-flight" response.
- Parasympathetic Nervous System: Responsible for the "rest-and-digest" response.

Sympathetic vs. Parasympathetic Nervous System

Sympathetic Nervous System:
- Prepares the body for action.
- Release of catecholamines (epinephrine and norepinephrine) from the adrenal medulla.
- Increased heart rate and contractility, blood pressure, and glucose release.
- Dilated pupils, bronchodilation, and decreased digestion and urination.
Parasympathetic Nervous System:
- Promotes relaxation and recovery.
- Release of acetylcholine.
- Decreased heart rate and contractility, blood pressure, and glucose release.
- Constriction of pupils, bronchoconstriction, and increased digestion and urination.

Increased Intracranial Pressure (ICP)

Increased pressure within the skull.
Caused by an increase in one of the intracranial components:
- **Stroke (hemorrhagic) **
- Tumor
- Inflammation (meningitis, encephalitis)
- Trauma
Normal ICP: 0-15 mmHg

Cerebral Perfusion Pressure (CPP)

Pressure needed for the brain to receive adequate blood flow.
Normal CPP: 40-100 mmHg
CPP Calculation: CPP = MAP - ICP
Mean Arterial Pressure (MAP) Calculation: MAP = SBP + (DBP x 2)/3
Normal MAP: 70-100mmHg

ICP Signs and Symptoms

Early Signs: Blurred vision, visual acuity, diplopia, change in LOC, restlessness to confusion, drowsiness, lethargy, pupillary changes, eye movement problems, hemiparesis, hemiplegia, headache.
Late Signs:
- BP: Increased systolic and decreased diastolic.
- Wide Pulse Pressure: Difference between systolic and diastolic (normal is 40, >60 is considered wide).
- Respiratory Rate: Irregular, Cheyne-Stokes hyperpnia (period of breathing followed by apnea).
- Temperature: Altered (may be high or low).

Signs of Meningitis

Kernig's Sign: Patient supine with hip flexed 90°, knee cannot be fully extended.
Brudzinski's Neck Sign: Neck rigidity, passive flexion of neck causes flexion of both legs and thighs.

Cerebral Hemorrhage

Ischemic Stroke: Partial or complete disruption of brain's blood supply due to thrombosis, embolism, or hemorrhage.
- Common Arteries: Middle Cerebral Artery (MCA), Internal Carotid Artery (ICA).
- Transient Ischemic Attacks (TIA): Warning sign of impending stroke.
Hemorrhagic Stroke: Hemorrhage, compartment syndrome (compression of nerves/arteries).
Signs: Headache, disorientation, confusion, decreased LOC.

Cerebral Embolism

Embolic stroke: Dislodged clot that travels to the brain.
Signs: Sudden onset of chest pain, syncope, headache, disorientation, confusion, decreased LOC.

Treatment for Cerebral Stroke

CT scan: Determines the type of stroke.
Cerebral Arteriography: Reveals the site and extent of the occlusion.
MRI: Shows damage to brain tissue.
Carotid UIZ: Shows plaque and blood flow of carotid arteries.
Endarterectomy: Removal of plaque from carotid arteries.
Echocardiogram: Finds clot source in the heart.

Seizures

Abnormal sudden, excessive discharge of electricity in cerebral cortex.
Types:
- Focal Seizures: Limited to one part of the brain, may only involve aura.
- Generalized Seizures: Involve the whole brain, may lead to loss of consciousness.
- Febrile Seizures: Most common in children.
Status Epilepticus: Continuous seizure activity for at least 5 minutes or more.
Priority: Airway, prevent aspiration, coma, and death.
Treatment: Diazepam, Dilantin (phenytoin), Thiamine.
Dx Tests: CT scan (brain lesion), EEG (hyperactive brain waves).

Multiple Sclerosis (MS)

Chronic autoimmune disease that destroys myelin sheath of neurons in CNS.
Symptoms: Charcot's Triad (optic nerve: blurring of vision, diplopia, scotomas, nystagmus; brainstem: dysarthria, cranial nerve 4 affected; motor pathways: tremors, ataxia, muscle weakness & spasms).
Other possible symptoms: Paresthesia, sensory loss, incontinence, impaired sexual ability, cognition issues, mood swings.
Dx Tests: CSF analysis (CSF protein, oligoclonal bands), MRI (demyelination).
Treatment:
- Supportive/palliative: Manage symptoms, prevent complications, avoid overheating.
- Acute exacerbation: Corticosteroids (prednisone, dexamethasone), corticotropin (ACTH).
- Chronic: Immunosuppressants (beta-interferon).

Alzheimer's Disease

Progressive, degenerative brain disease.
Common in women
Cause: Deficiency of Somatostatin, Acetylcholine, Norepinephrine, and Substance P.
Symptoms: Memory loss, amnesia, agnosia, apraxia, aphasia, ideation apraxia, receptive aphasia.
Dx Tests: CT scan, autopsy.
Treatment: Supportive/palliative, Donepezil (Aricept).

Parkinson's Disease

Progressive, degenerative disease.
Common in older adults.
Cause: Depletion of dopamine.
Symptoms: Resting tremor, rigidity, bradykinesia, postural instability, akinesia, mask-like facies, speech and swallowing difficulties.
Treatment:
- Supportive/palliative: Maintain siderails, turn pt Q2H, assist in passive ROM, increase fluid intake, high fiber diet, safety precautions, assist in ambulation, assist in surgery (Deep Brain Stimulation).
- Medications: Levodopa (L-Dopa) with Carbidopa, Amantadine, Artane, anticholinergics, iron supplement, vitamin C. Note that anti-Parkinsonian meds should be taken before meals to increase absorption.

Myasthenia Gravis

Chronic autoimmune disorder affecting voluntary muscles.
Involves impulse transmission at the neuromuscular junction.
More common in women
Cause: Idiopathic.
Symptoms: Ptosis, diplopia, mask-like facies, dysarthria, dysphagia, hoarseness, respiratory muscle weakness, leg weakness, fatigue.
Dx Test: Tensilon Test (Edrophonium chloride).
Crisis:
- Myasthenic Crisis: Caused by undermedication, stress, or infection.
- Cholinergic Crisis: Caused by overmedication.
Treatment:
- Supportive/palliative: Airway management, aspiration prevention, immobility, side rails, passive ROM exercises, NGT feeding, plasmapheresis, thymectomy.