Ophthalmology
Question 101 of 180
A 23 year old man presents to the Emergency Department complaining of visual disturbance. When a torch is shone into the right eye it elicits a direct reflex in right eye but no consensual reflex in left eye. Where is the lesion responsible for this finding?
Answer:
The right direct reflex is intact - when light is shone into the right eye, the right pupil constricts. The right afferent limb (right CN II), and the right efferent limb (right CN III) are both intact. The left consensual reflex is lost - when the right eye is stimulated by light, the left pupil does not constrict consensually. The right afferent limb is intact, but the left efferent limb (left CN III) is affected.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 |
