Ophthalmology
Question 58 of 97
A 43 year old woman presents to the Emergency Department complaining of vertical diplopia and difficulty walking downstairs. On examination you note the patient is tilting her head to the right. Loss of function of which of the following muscles is responsible for this presentation?
Answer:
The trochlear nerve innervates the superior oblique muscle, responsible for intorsion and depression of the eye. A trochlear nerve palsy leads to weakness of downward gaze causing difficulty walking downstairs or reading. The eye is extorted and may be elevated the patient tilts their head to compensate.Cranial Nerve Palsy
Neurology / Ophthalmology
Last Updated: 18th August 2022
Cranial nerve II: Optic nerve
| Cranial Nerve | Optic Nerve (CN II) |
|---|---|
| Key anatomy |
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| Function |
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| Assessment |
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| Clinical effects of injury |
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| Causes of injury |
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Cranial nerve III: Oculomotor nerve
| Cranial Nerve | Oculomotor Nerve (CN III) |
|---|---|
| Key anatomy |
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| Function |
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| Assessment |
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| Clinical effects of injury |
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| Causes of injury |
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Cranial nerve IV: Trochlear nerve
| Cranial Nerve | Trochlear Nerve (CN IV) |
|---|---|
| Key anatomy |
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| Function |
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| Assessment |
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| Clinical effects of injury |
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| Causes of injury |
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Cranial nerve VI: Abducens nerve
| Cranial Nerve | Abducens nerve (CN VI) |
|---|---|
| Key anatomy |
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| Function |
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| Assessment |
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| Clinical effects of injury |
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| Causes of injury |
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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 |
