Anatomy
Upper Limb
A patient presents following a road traffic collision. MRI imaging shows C7 - T1 disc herniation with C8 nerve root impingement. Where would the patient most likely complain of loss of sensation:
Answer:
The C8 dermatome extends over the medial arm, forearm and hand and is best tested on the little finger. The C8 nerve root is also responsible for flexion of the fingers.Dermatomal Supply of Upper Limb
Anatomy / Upper Limb / Innervation of Upper Limb
Last Updated: 29th January 2019
Table: Dermatomal Supply of the Upper Limb
| Dermatome | Landmark |
|---|---|
| C2 | Occipital Protuberance |
| C3 | Supraclavicular Fossa |
| C4 | Acromioclavicular Joint |
| C5 | Lateral Antecubital Fossa |
| C6 | Thumb |
| C7 | Middle Finger |
| C8 | Little Finger |
| T1 | Medial Antecubital Fossa |
| T2 | Apex of Axilla |
![By Grant, John Charles Boileau (An atlas of anatomy, / by regions 1962) [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/12/Dermatome-Body-Map-946x1024.png)
Dermatome Map. (Image by Grant, John Charles Boileau (An atlas of anatomy, / by regions 1962) [Public domain], via Wikimedia Commons)
The C2 dermatome is best tested at least one cm lateral to the occipital protuberance at the base of the skull. Alternately, it can be located at least 3 cm behind the ear.
The C3 dermatome is best tested in the supraclavicular fossa, at the midclavicular line.
The C4 dermatome is best tested over the acromioclavicular joint.
The C5 dermatome is best tested on the lateral (radial) side of the antecubital fossa just proximal to the elbow.
The C6 dermatome is best tested on the dorsal surface of the proximal phalanx of the thumb.
The C7 dermatome is best tested on the dorsal surface of the proximal phalanx of the middle finger.
The C8 dermatome is best tested on the dorsal surface of the proximal phalanx of the little finger.
The T1 dermatome is best tested on the medial (ulnar) side of the antecubital fossa, just proximal to the medial epicondyle of the humerus.
The T2 dermatome is best tested at the apex of the axilla.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
