Head, Neck and Spine (Part 1) Flashcards
What is the cranium?
The part of the skull enclosing the brain
How many cranial bones are there?
8
How are these different bonds joined / connected together?
Via sutures that develop throughout infancy and childhood (Therefore, a neonatal skull is different, in terms of the sutures are not fully formed)
How is an infant skull different to an adult skull (looking at the superior surface) and why is this difference important?
An area of unfused bone called the anterior fontanelle (junction of the sagittal suture, coronal suture, and frontal suture) - ‘soft spot’
Another area of unfused bone called the posterior fontanelle
This is important to allow some flexibility of the skull during birth, incase the birth canal is narrower than expected
When does the ‘soft spot’ on the babies head close up?
18-24 months
What is the facial skeleton?
The anterior part of the skull, bones making up the face
How many bones of the facial skeleton are there?
14
What are the names of the facial bones?
What are the cranial bones?
What is the suture / point where the sphenoid, frontal, temporal and parietal bones come together?
Pterion
What are the names of the junctions / sutures on the cranium?
Lambda is between the occipital and parietal bones
Coronal is between the frontal and parietal bones
Saggital is between the two parietal bones
Bregma is where the coronal and saggital sutures meet
Why is the pterion important clinically?
It is the weakest area on the skull, so a blow to the pterion could cause an intracranial bleed, which if not resolved can cause death
How can an intracranial bleed be fatal?
The pooling of blood in the skull increases the pressure on the brain as the skull is unable to expand, eventualling forcing the brain stem through the foramen magnum (big hole at the back bottom of the skull), causing brain stem death
What are fossae?
Shallow depressions (typically on the skull)
What are the cranial fossae when looking at the base of the skull?
Anterior cranial fossa where the frontal lobe sits
Middle cranial fossa where the temporal lobe sits
Posterior cranial fossa (in life covered by a layer of the meninges) where the cerebellum and brain stem sit
What are foramina?
Openings that allow the passage of structures from one region to another e.g. nerves
What are the cranial formamina when looking at the base of the skull?
What are cranial nerves and how many are there?
Pairs of nerves that connect the brain to different parts of the head, neck or trunk
12
What are the names of all 12 cranial nerves?
Olfactory nerve (CN I)
Optic nerve (CN II)
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Trigeminal nerve (CN V)
Abducens nerve (CN VI)
Facial nerve (CN VII)
Vestibulocochlear nerve (CN VIII)
Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
Accessory nerve (CN XI)
Hypoglossal nerve (CN XII)
What passes through the cribriform plate of ehtmoid?
Olfactory nerves (CN I) - from the top of the nose to the olfactory bulb in the brain
What passes through the optic canal?
Optic nerves (CN II)
What passes through the superior orbital fissure?
Occulomotor nerves (CN III) - involved in the control of the extrinsic muscles of the eye e.g. pupil dilation / constriction (muscles control the iris)
What passes through the foramen rotundum?
The maxillary division of the trigeminal nerve (CN V)
What passes through the foramen ovale?
The mandibular division of the trigeminal nerve (CN V)
What passes through the foramen sponisum?
Middle meningial artery to supple the dura around the brain
What passes through the internal acoustic meatus?
Facial nerves (CN VII) going to the muscles of the face and Vestibulocochlear nerves (VIII) going to the inner ear for balance and hearing
What passes through the jugular foramen?
Glossopharyngeal nerves (CN IX), Vagus nerves (X) and Accessory nerves (XI)
What passes through the hypoglossal canal?
Hypoglossal nerve (CN XII) - supplies the musculature of the tongue
What passes through the foramen magnum?
Joining of the spinal cord and brain stem (where they come together)
What are the meninges and why are they important structurally?
Membranes that cover the brain and line the skull
Stabilise and protect the brain
Why does the brain not have veins?
As the meninges form sinuses through which venous blood circulates in the cranial cavity
What are the 3 layers to the meninges and what are their properties?
Dura mater - thick and inelastic membrane composed of 2 layers (peiosteal, closely adherent to the inner table of the skull, and meningeal, close to the arachnoid)
Arachnoid mater - lies below the dura mater and is a more elastic membrane, and in the subarachnoid space, there are plenty of spider-like projections
Pia mater - innermost and most delicate layer, 2 cell thick surface to the brain (very thin)
Explain the different features of this diagram
Immediately attached to the inner table pf the skull if the periosteal layer of the dura, and to the arachnoid, the meningeal layer of the dura
Both layers of the dura are usually together, but when they split, they form the sinuses that contain the venous blood (superior saggital sinus is the biggest one)
The fold where the 2 dura layers come back together separates the two hemispheres of the brain (going down almost as far as the corpus collosum) and stabilise the brain
The cerebral spinal fluid is found in the subarachnoid space (between the spider-like projections) and bathes the brain to help protect it against movement and supply it nutrients
On the surface of the brain is the pia mater, and sometimes the arachnoid if the cerebral spinal fluid is drained away
How much space is between the dura and the bone in the cranial cavity?
How much space is between the dura and vertebral column (after coming out of the foramen magnum)?
None
Some space
What is an advantage, clinically, or having the extra space between the dura and vertebrae?
Good area to inject anaethesia e.g. epidurals in mothers for pain relief
What and where are the main folds of the dura?
2 major folds:
Falx cerebelli - the pink section in the diagram, it folds between the 2 hemispheres of the brain
Tentorium cerebelli - the purplish grey section in the diagram, it folds over the cerebellum (which sits in the posterior cranial fossa), and the gap in the middle is where the brain stem sits
Why are these major folds of the dura important?
Provides structural support for the brain, stopping it from moving around too much when the head shaken or hit
Which 2 of the 12 cranial nerves do not originate from the brain stem?
Olfactory nerve (CN I) and the Optic nerve (CN II)
Which cranial nerves have their nuclei located in the mid-brain?
Oculomotor nerve (CN III) and the Trochlear nerve CN (IV)
Which cranial nerves have their nuclei located within the pons (a structure within the brain stem)?
Trigeminal nerve (CN V), Abducens nerve (CN VI), Facial nerve (CN VII), and the vestibulocochlear nerve (CN VIII)
Which cranial nerves have their nuclei in the medulla oblongata?
Glossopharyngeal nerve (CN IX), Vagus nerve (CN X), Accessory nerve (CN XI), and the Hypoglossal nerve (CN XII)
What are the names and basic functions of all 12 cranial nerves?
Olfactory nerve (CN I) - sense of smell
Optic nerve (CN II) - vision acuity, visual fields, and pupillary light reflexes (afferent limb)
Oculomotor nerve (CN III) - all extrinsic eye muscles e.g. pupillary light reflexes (efferent limb), eyelid elevation, eye movements, except superior oblique and lateral recutus
Trochlear nerve (CN IV) - superior oblique, eye movements
Trigeminal nerve (CN V) - sensory to face, sinuses, teeth etc. and motor muscles of mastication (chewing)
Abducens nerve (CN VI) - lateral rectus, eye movements - abductions (move laterally away from the midline of the body)
Facial nerve (CN VII) - motor to muscles of facial expression, sensory taste and sensory to the external auditory meatus (ear canal opening) and nasopahrynx
Vestibulocochlear nerve (CN VIII) - sense of hearing and balance
Glossopharyngeal nerve (CN IX) - motor to sytlopharyngeus muscle, sensory taste, and mucosa of the nasopharynx and middle ear
Vagus nerve (CN X) - motor to vocal muscles, sensory from pharynx, larynx and lateral aspect of face, pparasympathetic innervation of the GI tract, heart and lungs
Accessory nerve (CN XI) - motor to sternocleidomastiod and trapezius
Hypoglossal nerve (CN XII) - motor to tongue muscle
What are the steps to introducing yourself and asking for consent from a patient when conducting an examination?
- Full name
- Role e.g. medical student (from ICL)
- Confirm patient’s name and DOB
- Explain purpose first, then ask for consent i.e. what’s going to be examined and why
- State patient exposure and posture i.e. whether they need to take any clothing off, and how they should sit / stand / lie
- Ask if the patient is in any pain
- Wash hands
What is the function of the Olfactory nerve and what is its anatomical course?
A specialised sensory nerve - transmits information relating to the sense of smell
Olfactory receptors in the nasal epithelium detect smells and transmit them along their axons forming the olfactory nerves
It passes through the intra-cranial cavity through the cribriform plate in the ethmoid bone
Ultimately reaches the primary olfactory cortex in the temporal lobe of the brain
How can the Olfactory nerve (CN I) ‘s function be tested for clinically?
- Ask the patient if they have noticed any changes in their sense of smell
- Use a common, strong scent to test their smell e.g. lemon, lavender, mint … etc.
- Test each nostril separately (by asking the atient to press down on one of their nostrils) and ask the patient to close their eyes before giving them the scent
What does a lack in sense of smell point to clinically?
Loss of smell is called anosmia
If it is temporary, usually due to a common cold or other upper respiratory tract infections
If it is permanent, it may be due to severe head injuries or tumours that run along the olfactory nerves
If it is progressive, it may be due to neuro degenerative diseases, such as Alzheimer’s or some other brain disorders (such as multiple sclerosis)
What is the nerve function of the Optic nerve (CN II) and its anatomical course?
The afferent limb of the pupillary light reflex
Light is detected by rods and cones, and converted into impulses, which travel along the retina through the intracranial / optic cavity to the brain
They pass through the visual pathway within the brain to the primary visual cortex
The pupillary reflex action is faster, hence takes a shorter pathway - sensory impulses sent via mid brain nuclei to trigger motor impulses through parasympathetic axons in the oculomotor nerves (efferent limb) to innervate the pupillary sphincter muscles in the eye leading to pupillary constriction (miosis)
Leads to miosis of the ipsilateral pupil (same side) and the contralateral pupil (other side)
How can the Optic nerve (CN II) and Oculomotor nerve (CN III) ‘s function be tested for clinically?
- Ask the patient for consent
- Ask them to keep their headyb still and to look at a distant target
- Inspect the pupils for size, shape and colour and any presence of ptosis (drooping of eye lid)
- Shine one eye with a penlight - observe for ipsilateral pupillary constriction (in the same eye)
- Take away the light for a few seconds
- Shine the penlight in the same eye - observe for the consensual pupillary constriction (in the other eye)
Label the living anatomy of the eye?
Why is it important to inspect the pupils in ambient light first before applying the light for the Optic nerve (CN II) test?
About 20% of the population suffer from anisocoria - unequal size of the eyes’ pupils
May be a long term, entirely harmless finding
May point to more serious damage, especially if the person is drowsy or unconscious
What does an abnormal pupillary reflex point to clinically?
As this test assesses the integrity of the function of both, the optic and oculomotor nerves, damage to these nerves, the brainstem or depressant drugs may cause abnormalities
What are some other ways of testing for the Optic nerve (CN II)?
Peripheral visual fields
Blind spot
Visual Acuity
Colour vision
