Anatomy
Upper Limb
You are reviewing a patient following a fall from a horse. You suspect they may have an Erb's palsy as a result of a brachial plexus injury. Regarding Erb's palsy, which one of the following statements is CORRECT:
Answer:
Erb's palsy is caused by damage to the C5 and C6 nerve roots and thus primarily involves the musculocutaneous, suprascapular and axillary nerves. It commonly result from an excessive increase in the angle between the neck and the shoulder e.g. a person thrown from a motorbike or horseback or during a difficult birth. There is loss or weakness of abduction, lateral rotation and flexion of the arm and flexion and supination of the forearm and loss of sensation on the lateral arm. A characteristic 'Waiter's tip' deformity may be present where the limb hangs limply by the side, medially rotated by the unopposed action of pectoralis major with the forearm pronated due to paralysis of the biceps brachii.Brachial Plexus Injury
Anatomy / Upper Limb / Innervation of Upper Limb
Last Updated: 8th April 2019
Brachial plexus injuries are usually the result of blunt trauma producing nerve avulsions and disruption.
Table: Clinical Features of Brachial Plexus Injury
| Brachial plexus injury | Erb’s palsy | Klumpke’s palsy |
|---|---|---|
| Mechanism of injury | Excessive increase in angle between neck and shoulder e.g. during breech delivery or from fall from motorbike or horse | Sudden excessive abduction e.g. person catching something overhead as they fall or during a difficult delivery |
| Nerve roots affected | C5, C6 | C8, T1 |
| Nerves affected | Musculocutaneous, axillary, suprascapular and nerve to subclavius | Ulnar and median nerves |
| Muscles affected | Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor | All small muscles of hand (flexor muscles in forearm innervated by different nerve roots) |
| Motor loss | Abduction, flexion and lateral rotation of arm, flexion and supination of forearm | Intrinsic hand movements |
| Sensory loss | Lateral arm | Medial arm |
| Deformities | Waiter’s tip | Claw hand |
Klumpke's Palsy
Klumpke's palsy affects nerves derived from the C8 or T1 roots. It is much less common than Erb's palsy. It usually occurs from sudden excessive abduction of the arm e.g. catching something overhead when falling, or during a difficult birth. All the small muscles of the hand are affected (the flexor muscles of the forearm are spared as they are supplied by different roots). There is sensory loss over the medial side of the arm and a characteristic 'claw hand' appearance, where the metacarpophalangeal joints are hyperextended, and the interphalangeal joints are flexed.
Erb's Palsy
Erb's palsy affects nerves derived from the C5 or C6 roots. It commonly result from an excessive increase in the angle between the neck and the shoulder e.g. a person thrown from a motorbike or horseback or during a difficult birth. There is loss or weakness of abduction, lateral rotation and flexion of the arm and flexion and supination of the forearm and loss of sensation on the lateral arm. A characteristic 'Waiter's tip' deformity may be present where the limb hangs limply by the side, medially rotated by the unopposed action of the pectoralis major with the forearm pronated and extended and the wrist flexed.
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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 |
