Anatomy
Central Nervous System
A 31 year old male presents to ED with a head injury. Rhinorrhoea will most likely result from fracture of which of the following bones:
Answer:
Rhinorrhoea will most likely result from a fracture of the cribriform plate of the ethmoid bone, which can tear the arachnoid membrane and result in leakage of CSF into the nasal cavity.Cerebrospinal Fluid
Anatomy / Central Nervous System
Last Updated: 11th April 2019
Total CSF volume is about 130 ml, of which the majority is in the subarachnoid space.
Function
CSF has three main functions:
- Protection - acting as a cushion for the brain
- Buoyancy - reducing the net weight of the brain to prevent excessive pressure on the base of the brain
- Chemical stability - creating the right chemical environment to allow proper functioning of the brain
Production
CSF is secreted by the ventricular choroid plexuses, which are vascular conglomerates of capillaries, pial and ependymal cells. The majority of CSF arises from the plexuses of the lateral ventricles.
Flow
From the lateral ventricles, CSF passes through the interventricular foramina to the third ventricle, then the cerebral aqueduct to the fourth ventricle.
From the roof of the fourth ventricle, the CSF drains via foramina into the central spinal canal (bathing the spinal cord) and the subarachnoid cisterns in the subarachnoid space located between the arachnoid mater and pia mater (bathing the brain).
From the subarachnoid cisterns, CSF is reabsorbed by arachnoid granulations, which protrude into the dura mater, into the dural venous sinuses and from here back into the circulation.
There is small but significant CSF drainage via the cribriform plate of the ethmoid into the nasal tissues. Fracture of the cribriform plate results in CSF rhinorrhoea.
Circulation of Cerebrospinal Fluid. (Image by OpenStax [CC BY 4.0 , via Wikimedia Commons)
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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 |
