Anatomy
Cranial Nerve Lesions
A 64 year old lady presents to ED with headaches. Imaging show a tumour compressing the structures in the internal auditory meatus. Which of the following structures are most likely affected:
Answer:
The internal auditory meatus transmits the facial and vestibulocochlear nerves.Cranial Nerve Overview
Anatomy / Central Nervous System / Cranial Nerve Lesions
Last Updated: 24th February 2019
There are 12 pairs of cranial nerves arising from the brain.
| Cranial Nerve | Origin | Exit from Skull | Function |
|---|---|---|---|
| Olfactory Nerve (I) | Cerebrum | Cribriform Plate | SA: smell |
| Optic Nerve (II) | Cerebrum | Optic Canal | SA: vision |
| Oculomotor Nerve (III) | Midbrain | Superior Orbital Fissure | GSE: levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, inferior oblique
GVE: sphincter pupillae, ciliary muscles |
| Trochlear Nerve (IV) | Midbrain | Superior Orbital Fissure | GSE: superior oblique |
| Trigeminal Nerve (V): | Pons | Superior Orbital Fissure (V1); Foramen Rotundum (V2); Foramen Ovale (V3) | GSA: sensory from most of head
BE: temporalis, masseter, medial and lateral pterygoids, tensor tympani, tensor veli palatini, anterior belly of digastric, mylohyoid |
| Abducens Nerve (VI) | Pons | Superior Orbital Fissure | GSE: lateral rectus |
| Facial Nerve (VII) | Pons | Internal Acoustic Meatus; Stylomastoid Foramen | GSA: sensory from external acoustic meatus and skin posterior to ear
SA: taste from anterior two-thirds of tongue GVE: lacrimal gland, submandibular and sublingual salivary glands, mucous membranes of nasal cavity and palate BE: muscles of face and scalp, stapedius, posterior belly of digastric, stylohyoid |
| Vestibulocochlear Nerve (VIII) | Pons | Internal Acoustic Meatus | SA: balance and hearing |
| Glossopharyngeal Nerve (IX) | Medulla | Jugular Foramen | GVA: sensory from carotid body and sinus, posterior one-third of tongue, palatine tonsils, upper pharynx, and mucosa of middle ear and pharyngotympanic tube
SA: taste from posterior one-third of tongue GVE: parotid salivary gland BE: stylopharyngeus |
| Vagus Nerve (X) | Medulla | Jugular Foramen | GSA: sensory from skin posterior to ear and external acoustic meatus, and dura in posterior cranial fossa
GVA: sensory from aortic body chemoreceptors and aortic arch baroreceptors, mucous membranes of pharynx, larynx, oesophagus, bronchi, lungs, heart, and abdominal viscera of foregut and midgut SA: taste from epiglottis GVE: smooth muscle and glands in pharynx, larynx, thoracic viscera and abdominal viscera in foregut and midgut BE: palatoglossus, muscles of soft palate (except tensor veli palatini), muscles of pharynx (except stylopharyngeus), muscles of larynx |
| Spinal Accessory Nerve (XI) | Medulla | Jugular Foramen | BE: sternocleidomastoid and trapezius |
| Hypoglossal Nerve (XII) | Medulla | Hypoglossal Canal | GSE: hyoglossus, genioglossus, styloglossus and intrinsic muscles of tongue |
(GSA = General Somatic Afferent; GVA = General Visceral Afferent; SA = Special Afferent; GSE = General Somatic Efferent; GVE: General Visceral Efferent; BE = Branchial Efferent)
Cranial Nerve Origins (Left) and Cranial Nerve Exits (Right). (Image modified by FRCEM Success. Original by Patrick J. Lynch, medical illustrator (Patrick J. Lynch, medical illustrator) [CC BY 2.5 , 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 |
