Updated: 2/11/2019

Ulnar nerve

Review Topic
Origin of Ulnar Nerve
  • Ulnar nerve comes from the medial  cord of the brachial plexus (C8-T1)
Course of Ulnar Nerve
  • Lies posteromedial to brachial artery in anterior compartment of upper 1/2 arm
  • Pierces medial IM septa at the arcade of Struthers ~ 8cm from medial epicondyle and lies with triceps
  • Travels on back of medial epicondyle; vulnerable in fractures
    •  Runs with superior ulnar collateral artery
    • Cubital tunnel
      • roof - cubital tunnel retinaculum (medial epicondyle to olecranon) / osbourne’s fascia (extension of deep forearm fascia between heads of FCU)
      • floor - posterior and transverse bands of MCL
  •  Does send small sensory branch to elbow that can be sacrificed
  • Passes into forearm between 2 heads of flexor carpi ulnaris
  • Runs between FCU + FDP
  • At the wrist, the ulnar nerve and artery pass superficial to the flexor retinaculum
Motor Innervation of Ulnar Nerve
  • motor
    • forearm
      • flexor carpi ulnaris
      • flexor digitorum profundus III and IV
    • thenar
      • adductor pollicis
      • deep head of flexor pollicis brevis (FPB)
    • fingers
      • dorsal interosseous & palmar interosseous
      • 3rd & 4th lumbrical (1st & 2nd by median nerve)
    • digiti minimi
      • abductor digiti minimi
      • opponens digiti minimi
      • flexor digiti minimi
  • sensory branches of ulnar nerve
    • dorsal cutaneous branch
    • palmar cutaneous branch
    • superficial terminal branches
Clinical Conditions
  •  Cubital Tunnel Syndrome compression sites
    • Arcade of Struthers (tunnel 8 cm proximal to medial epicondyle formed by fibrous connection between IM septum and medial head of triceps)
    • medial intermuscular septum
    • medial epicondyle (osteophytes)
    • cubital tunnel retinaculum (taught with flexion)
      • often the retinaculum is consistent with Osborne’s ligament
    • aponeurosis of the two heads of the FCU (arcuate ligament) is often consistent with the retinaculum and osbournes ligament, however these fibers meet perpendicular to retinaculum/osbournes ligament
    • deep flexor/pronator aponeurosis (most distal site - approximately 4 cm distal to medial epicondyle)
    • The internal anatomy of the ulnar n can explain the predominance of hand sx from cubital tunnel syndrome – the fibers to FCU and FDP are central and hand intrinsic fibers are peripheral!
  • Ulnar tunnel syndrome: compression in Guyon’s Canal
    • no involvement of dorsal cutaneous nerve since it branches before canal
    • no involvement of  FDP of 4th & 5th and FCU
    • ganglia most common cause (from triquetrohamate joint, 32-48%)
    • other causes: other mass, trauma (Distal radius/ulna, hook of hamate), muscle anomaly, ulnar artery aneurysm
    • Zones of compression
      • Zone 1: proximal to bifurcation: hook of hamate fx & ganglia, motor & sensory findings
      • Zone 2:  deep motor branch; hook of hamate fx & ganglia, motor sx
      • Zone 3:  superficial sensory branch; ulnar artery thrombosis

Ulnar Nerve


Please rate topic.

Average 5.0 of 1 Ratings

Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine

The complexity of this topic is appropriate for?
How important is this topic for board examinations?
How important is this topic for clinical practice?
Questions (1)
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
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
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

(M1.AN.4707) A 12-year-old boy presents to the emergency department with severe right elbow pain after falling off his bicycle. His mother says that he was otherwise healthy prior to the fall and does not take any medications. Upon physical exam he has pain over the medial side of his elbow and had limited range of motion due to pain. He has loss of digit flexion and decreased sensation over his medial 1 and ½ fingers. Which of the nerves shown in Figure A is most likely to be affected in this patient? Review Topic

QID: 108425





















Select Answer to see Preferred Response

Topic COMMENTS (0)
Private Note