Updated: 3/8/2019

Cranial Nerves

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Overview

Cranial nerves illustration

Illustration by Ava Yap

 
Snapshot
  • A 35-year-old woman presents to the emergency department with left eye vision loss and headache. She was in her usual state of health until 3 hours prior to presentation, when she developed vision loss and eye pain that worsened with eye movement. She reports that approximately 8 months ago she had left arm numbness that self resolved. On physical exam, her visual acuity is 20/185, and a sluggish response to light on the left eye with the swinging flash-light test is noted. (Optic neuritis likely secondary to multiple sclerosis.)
Introduction
 
Cranial Nerves
Cranial Nerve Type Function Cranial Exit
Notes
  • Olfactory nerve (I)
  • Sensory
  • Olfaction
  • Cribiform plate
  • Only CN without thalamic relay to the cortex                        
  • Optic nerve (II)
  • Sensory
  • Vision
  • Optic canal
-
  • Oculomotor nerve (III)
  • Motor
  • Eye movement via the
    • superior, inferior, and medial rectus
    • inferior oblique muscle
  • Pupillary constriction
  • Accomodation
  • Eyelid opening via innervation of the
    • levator palpebrae muscle
  • Superior orbital fissue
  • Center contains output to ocular muscles which is affected primarily 1st by vascular disease
  • Periphery contains parasympathetic output which is affected 1st by compression
  • Trochlear nerve (IV)
  • Motor
  • Eye movement via innervation of the
    • superior oblique muscle
  • Superior orbital fissue
-
  • Trigeminal nerve (V)
  • Motor and sensory
  • Mastication via the mandibular nerve (V3)
  • Facial sensation via the
    • ophthalmic nerve (V1)
    • maxillary nerve (V2)
    • mandibular (V3)
  • Ophthalmic nerve (V1)
    • superior orbital fissure
  • Maxillary nerve (V2)
    • foramen rotundum 
  • Mandibular nerve (V3)
    • foramen ovale
-
  • Abducens nerve (VI)
  • Motor
  • Eye movement via innervation of the
    • lateral rectus
  • Superior orbital fissure
-
  • Facial nerve (VII)
  • Motor and sensory
  • Facial movement
  • Taste from the anterior 2/3 of tongue
  • Lacrimation
  • Salivation via innervation of the
    • submandibular gland
    • sublingual gland
  • Eyelid closing via innervation of the 
    • orbicularis oculi muscle
  • Stapedius 
    • dampens excessive sound
  • Internal auditory meatus 
  • Visceral sensation recieved by nucleus solitarius
  • Vestibulocochlear nerve (VIII)
  • Sensory
  • Hearing
  • Balance
  • Internal auditory meatus 
-
  • Glossopharyngeal nerve (IX)
  • Motor and sensory
  • Taste from posterior 1/3 of tongue
  • Swallowing
  • Salivation 
    • parotid gland
  • Monitoring carotid body and sinus chemo- and baroreceptors
  • Stylopharngeus
    • elevates pharynx and larynx
  • Jugular foramen
  • Motor output orginates in nucleus ambiguus
  • Visceral sensation recieved by nucleus solitarius
  • Vagus nerve (X)
  • Motor and sensory
  • Taste from epiglottic region
  • Swallowing
  • Palate elevation
  • Midline uvula
  • Talking
  • Coughing
  • Thoracoabdominal viscera
  • Monitoring aortic arch chemo- and baroreceptors
  • Stimulation of auricular branch can cause vasovagal syncope
  • Jugular foramen
  • Motor output orginates in nucleus ambiguus
  • Visceral sensation recieved by nucleus solitarius
  • Parasympathetic fibers to heart, lungs, and upper GI orginates from dorsal motor nucleus
  • Gives recurrent laryngeal nerve which innervates all laryngeal muscles except cricothyroid
  • Accessory nerve (XI)
  • Motor
  • Head turning and shoulder shrugging
    • sternocleidomastoid muscle
    • trapezius
  • Jugular foramen
  • Motor output orginates in nucleus ambiguus
  • Hypoglossal nerve (XII)
  • Motor
  • Tongue movement
  • Hypoglossal canal
-
 
 

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Questions (11)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.NE.4756) A 4-year-old male is accompanied by his mother to a head and neck surgeon for a follow-up visit after the patient underwent a branchial cyst operation. The child’s immediate post-operative period was uneventful. However, the mother reports that the child has had trouble speaking since the operation. His words appear more slurred than before. The child’s pain has been well controlled with acetaminophen. The child was born at 34 weeks’ gestation and stayed one day in the neonatal intensive care unit for prematurity prior to being discharged without any abnormal findings. On examination, the incision is clean, dry, non-erythematous, and shows signs of healing. The child is asked to stick out his tongue and findings are shown in Figure A. Which of the following muscles is most likely affected in this patient? Review Topic

QID: 108926
FIGURES:
1

Mylohyoid

9%

(21/223)

2

Palatoglossus

18%

(40/223)

3

Genioglossus

52%

(115/223)

4

Stylohyoid

7%

(15/223)

5

Stylopharyngeus

8%

(17/223)

M1

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(M1.NE.41) A 45-year-old man is brought to the emergency department after being found down in the middle of the street. Bystanders reported to the police that they had seen the man as he exited a local bar, and he was subsequently assaulted. He sustained severe facial trauma, including multiple lacerations and facial bone fractures. The man is taken to the operating room by the ENT team, who attempt to reconstruct his facial bones with multiple plates and screws. Several days later, he complains of the inability to open his mouth wide or to completely chew his food, both of which he seemed able to do prior to surgery. Which of the following is a characteristic of the injured nerve branch? Review Topic

QID: 106262
1

Sensory component only

3%

(3/119)

2

Voluntary motor component only

27%

(32/119)

3

Voluntary motor and sensory components

66%

(79/119)

4

Parasympathetic component only

2%

(2/119)

5

Sympathetic component only

0%

(0/119)

M1

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PREFERRED RESPONSE 3

(M1.NE.26) Where does the only cranial nerve without a thalamic relay nucleus enter the skull? Review Topic

QID: 101690
1

Foramen rotundum

4%

(5/137)

2

Jugular foramen

3%

(4/137)

3

Internal auditory meatus

2%

(3/137)

4

Superior orbital fissure

2%

(3/137)

5

Cribriform plate

87%

(119/137)

M1

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(M1.NE.40) A 45-year-old man is brought to the emergency department after being found down in the middle of the street. Bystanders reported to the police that they had seen the man as he exited a local bar, where he was subsequently assaulted. He sustained severe facial trauma, including multiple lacerations and facial bone fractures. The man is taken to the operating room by the ENT team, who attempted to reconstruct his facial bones with multiple plates and screws. Several days later, he complains of the inability to open his mouth wide or to completely chew his food, both of which he seemed able to do prior to the surgery. Where does the affected nerve exit the skull? Review Topic

QID: 106268
1

Foramen ovale

50%

(118/236)

2

Foramen rotundum

15%

(36/236)

3

Superior orbital fissue

6%

(15/236)

4

Jugular foramen

15%

(36/236)

5

Inferior orbital fissue

8%

(19/236)

M1

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PREFERRED RESPONSE 1
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