Updated: 7/10/2018

Spinal Cord

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Overview
                     
Snapshot
  • A 26-year-old male presents with lower back pain that radiates down the side of his right leg and into his right foot. The pain started after he was recently lifting furniture into his new home. On physical exam, there is notable weakness on dorsiflexion of the foot and extension of the toe. Sensory loss is noted between the first and second digit of the foot. Knee and ankle reflexes are normal. There is no saddle anesthesia, and anal wink is appreciated. When raising the extended leg while in the supine position, pain radiates from the lower back, down the leg, and into the foot. (L5 radiculopathy due to disc herniation)
Introduction
  • Spinal nerves  
    • 31 pairs
      • 8 cervical
      • 12 thoracic
      • 5 lumbar
      • 5 sacral
      • 1 coccygeal
    • vertebral exit
      • C1-C7 exit via intervertebral foramina above corresponding vertebra
      • all other nerves exit via intervertebral foramina below corresponding vertebra
  • Spinal cord termination
    • adults
      • spinal cord ends at L1-L2
        • becomes cauda equina
      • subarachnoid space extends to lower border of S2
      • see Lumbar puncture topic
  • Pathology
    • vertebral disk herniation
      • nucleus pulposus herniates posteriolaterally through annulus fibrosis
      • most commonly occurs between L5 and S1 
      • cauda equina affects S2-S5 nerve roots 
Spinal Cord Pathways
  • Sensory pathways
    • dorsal columns
      • function
        • ascending pressure, vibration, discriminative touch, and proprioceptive sensation
      • subdivisions
        • fasciculus cuneatus
          • upper body and extremities
        • fasciculus gracilis
          • lower body and extremities
      • pathway
        • 1st order neuron
          • sensory nerve ending → dorsal root ganglion (location of cell body) → spinal cord → ipsilateral ascent in dorsal column → synapse in ipsilateral nucleus in medulla (cuneatus or gracilis)
        • 2nd order neuron
          • ipsilateral nucleus in medulla → decussates in medulla → contralateral ascent in medial lemniscus → synapse in VPL of thalamus
        • 3rd order neuron
          • VPL of thalamus → sensory cortex
    • Spinothalamic tract
      • function
        • ascending pain and temperature sensation 
      • pathway
        • 1st order neuron
          • sensory nerve ending → dorsal root ganglion (location of cell body) → spinal cord → synapse in ipsilateral gray matter of spinal cord
        • 2nd order neuron
          • ipsilateral gray matter of spinal cord → decussates at anterior white commissure → contralateral ascent in spinothalamic tract → synapse in VPL of thalamus
        • 3rd order neuron
          • VPL of thalamus → sensory cortex
  • Motor pathways
    • lateral corticospinal tract   
      • function
        • descending voluntary motor control of contralateral limbs
      • pathway
        • 1st order neuron (upper motor neuron)
          • cell body in primary motor cortex → ipsilateral descent through internal capsule → decussation at caudal medulla (pyramidal decussation) → contralateral descent in lateral corticospinal tract → synapse at cell body of anterior horn in spinal cord
        • 2nd order neuron (lower motor neuron)
          • leaves anterior horn of spinal cord → synapses at neuromuscular junction
 
 

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Questions (6)
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.77) A patient with a known spinal cord ependymoma presents to his neurologist for a check up. He complains that he has had difficulty walking, which he attributes to left leg weakness. On exam, he is noted to have 1/5 strength in his left lower extremity, as well as decreased vibration and position sensation in the left lower extremity and decreased pain and temperature sensation in the right lower extremity. Which of the following spinal cord lesions is most consistent with his presentation? Review Topic

QID: 106882
1

Left-sided Brown-Sequard (hemisection)

82%

(14/17)

2

Right-sided Brown-Sequard (hemisection)

12%

(2/17)

3

Anterior cord syndrome

0%

(0/17)

4

Posterior cord syndrome

6%

(1/17)

5

Syringomelia

0%

(0/17)

M1

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