Ophthalmology
Question 23 of 97
A 34 year old man presents with an acute onset of diplopia. On examination you note the right eye is looking downward and outward at rest. Which cranial nerve is responsible for this abnormality?
Answer:
"Down and out" position of the eye at rest is due to paralysis of the superior, inferior and medial rectus, and the inferior oblique. These muscles are innervated by the oculomotor nerve. There is unopposed activity of the lateral rectus and superior oblique causing the "down and out" position.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 |
