📚 Question Bank

The given clinical scenario is suggestive of cauda equina syndrome. The conus medullaris syndrome typically shows the symmetrical weakness of lower limbs, whereas the cauda equina syndrome, presents with asymmetrical weakness of lower limbs.

Radicular pain, lower motor neuron injury, and urinary retention are common to both conus medullaris and cauda equina syndrome.

In anterior plagiocephaly, the premature fusion of the coronal sutures is seen. The coronal suture is present between the frontal and parietal bones.

Major sutures of the skull are:

• Lambdoid suture - between parietal and occipital bones.
• Sagittal suture - between the two parietal bones.
• Metopic suture - between the two frontal bones.

Craniosynostosis consists of premature fusion of one or more cranial sutures, resulting in an abnormal head shape.

The foramen marked is the foramen spinosum. The structures passing through it are:

• Middle meningeal artery
• Nervus spinosus
• Middle meningeal vein

ˆernet's syndrome or jugular foramen syndrome refers to the palsies of IX, X, and XI cranial nerves traversing the jugular foramen. The sigmoid sinus passes through the posterior aspect of the jugular foramen.

Jugular foramen can be divided into three compartments:

• Anterior - Inferior petrosal sinus
• Intermediate - CN IX, X, XI
• Posterior - Sigmoid sinus continuing as the internal jugular vein

The arteries passing through the foramen are the meningeal branch of ascending pharyngeal artery and the meningeal branch of the occipital artery. çmissary veins may also traverse it.

The membrana tectoria of atlanto-axial joint passes through the foramen magnum.

Certain structures pass through two compartments of the foramen magnum -

the osseo-ligamentous (anterior) and neuro-vascular (posterior) compartments - as shown in the image below:

The X-ray shows a fracture of the floor of the orbit. The maximum contribution to the floor of the orbit is by the maxilla.

Boundaries of the bony orbit:

• Roof:
• Orbital plate of frontal bone
• Sphenoid bone (small part)
• Floor: Thin plate of bone that also forms the roof of the maxillary sinus
• Orbital plate of maxilla
• Zygomatic bone (anterolateral)
• Orbital process of palatine bone (posteromedial)
• Medial wall:
• Maxilla
• Lacrimal bone
• Ethmoid bone
• Sphenoid bone
• Lateral wall:
• Zygomatic bone (anterior)
• Greater wing of sphenoid (posterior)
• Sphenozygomatic suture.

The orbital floor can be fractured by trauma to the orbit as seen in falls, motor vehicle accidents, and assaults. The image given shows X-ray Water's view with a 'teardrop' sign. The orbital contents leak out of the fractured orbital floor, giving it a teardrop-like appearance.

Upper eyelid lacerations are sutured under supraorbital nerve block. The anesthesia is achieved by approaching the nerve at the supraorbital foramen/notch. The supraorbital notch is present at the junction of lateral two-third and medial one-third of the supraorbital margin (point C). It transmits the supraorbital nerve and vessels.

An extradural hematoma at the pterion is a result of an injury of the anterior division of the middle meningeal artery.

The pterion is an H-shaped sutural junction between four bones of the skull:

• Frontal bone
• Squamous part of the temporal bone
• Greater wing of sphenoid bone
• Parietal bone.

It also overlies the lateral fissure of the cerebral hemisphere, the hematoma can cause compressive lesions here.

The infection has likely spread from the sub-aponeurotic tissue.

The sub-aponeurotic loose areolar tissue of the scalp is referred to as the dangerous area of the scalp. Infection from this layer can pass into the cranial cavity through small emissary veins, which pass through parietal foramina in the calvaria. It can reach intracranial structures causing meningitis and intracranial abscesses.

The scalp is a soft tissue that covers the calvaria of the skull. It consists of 5 layers as shown in the image below (mnemonic - SCALP):

The following are some muscles of facial expression and their actions:

• Orbicularis oculi - Closing eyelids
• Risorius - Retracts angle of the mouth, grinning muscle
• Orbicularis oris - Closes mouth
• Mentalis - wrinkles chin
• Corrugator supercilli - frowning
• Zygomaticus major - smiling and laughing
• Depressor anguli oris - depresses angle of mouth
• Levator labii superioris - elevates upper lip
• Depressor labii inferioris - depresses lower lip
• Buccinator - known as whistling muscle, it flattens the cheeks against the gums and teeth
• Note: Modiolus is a fibromuscular structure formed by the interlacing of 5 muscles.

The buccinator muscle is involved in flattening the cheeks against the gums and teeth. Hence, it is known as the whistling muscle. The buccal branch of the facial nerve innervates the buccinator

muscle but does not pierce it.

The structures piercing the buccinator muscle are:

• Parotid duct
• Buccal branch of the mandibular nerve
• Molar mucous glands which lie on the buccopharyngeal fascia around the parotid duct

Carotid bruit is identified by auscultating the carotid artery, which is located in the carotid triangle. The mylohyoid muscle does not form the floor of the carotid triangle.

Floor:

• Thyrohyoid
• Hyoglossus
• Middle constrictor
• Inferior constrictor
• Roof:
• Skin
• Superficial fascia
• Platysma
• Deep fascia containing branches of facial and cutaneous cervical nerves.
• Posterior border:
• Sternocleidomastoid muscle
• Anteroinferior border:
• The superior belly of omohyoid
• Superior border:
• Posterior belly of digastric
• Stylohyoid

In the given scenario, the patient most likely suffered an iatrogenic injury to the spinal accessory nerve as it is placed superficially in the middle of the posterior triangle, therefore the actions of trapezius and sternocleidomastoid can be affected. Adduction of the arm will be intact here, as this action is caused by pectoralis major which is supplied by the medial and lateral pectoral nerves.

Injury to the spinal accessory nerve affects the movements of the muscles supplied by it. They are:

• Trapezius - overhead abduction, elevation, and retraction of scapula. It is tested by asking the patient to shrug the shoulders.
• Sternocleidomastoid - turning the chin to the opposite side, tilting the head towards the shoulder of the same side. When both act together they draw the head forwards.

The spinal accessory nerve innervates the sternocleidomastoid just before entering the posterior triangle.

• If the nerve is injured before it enters the posterior triangle, actions of the sternocleidomastoid will be affected.
• If the nerve is injured within the posterior triangle, the sternocleidomastoid will be spared.

Roseola infantum is a viral fever caused by human herpesvirus 6 and 7. It presents with fever, rash, cervical and occipital lymphadenopathy. These lymph nodes are present in the occipital triangle. Nerve to rhomboids is a content of the occipital triangle.

Contents of the occipital triangle are:

• Occipital lymph nodes
• Nerve to rhomboids
• Spinal accessory nerve
• Lesser occipital nerve
• Great auricular nerve
• Supraclavicular nerves
• Muscular branches to levator scapulae and trapezius
• Uppermost part of brachial plexus
• Transverse cervical artery
• Occipital artery

The given clinical scenario of ptosis, miosis, and anhydrosis is suggestive of Horner's syndrome which can be caused by damage to the cervical sympathetic trunk (marked B).

In the given image:

• Vagus nerve
• Cervical sympathetic trunk
• Phrenic nerve
• Recurrent laryngeal nerve

The cervical part of the sympathetic trunk lies anterior to longus colli and longus capitis muscles (enclosed in prevertebral fascia) and posterior to the common carotid artery. The sympathetic trunk lies outside the carotid sheath.

The marked area on the mandible is the pterygoid fovea where the lateral pterygoid muscle is inserted. The action of this muscle is depression, protrusion, and side to side movement of the jaw.

Lateral pterygoid muscle:

• Origin - Upper head arises from the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone. The lower head arises from the lateral surface of the lateral pterygoid plate.
• Insertion - It is inserted into the pterygoid fovea, the capsule of the temporomandibular joint, and the articular disc.

Anterior temporomandibular joint (TMJ) dislocation occurs due to the excessive contraction of the lateral pterygoid. It is associated with the extreme opening of mouth such as yawning, laughing, vomiting or dental treatment.

Some fibres of the upper head of the lateral pterygoid are inserted into the capsule of the TMJ and to the anterior and medial borders of the articular disc. Hence, its contraction can exert forward traction on the disc, allowing for jaw protrusion and in extreme cases, the anterior displacement of the TMJ.

Superior and posterior dislocations of TMJ are rare and is associated with high-energy trauma.

The given clinical scenario with a history of chickenpox and lesions over the face is suggestive of herpes zoster ophthalmicus. The cranial nerve involved is the trigeminal nerve. Motor innervation is exclusively carried by mandibular division, not the maxillary division.

The trigeminal nerve (CNV) is the largest cranial nerve. It is a predominantly sensory nerve with motor components.

The nerve divides into three divisions:

• Ophthalmic nerve - V1
• Maxillary nerve - V2
• Mandibular nerve - V3

Ophthalmic nerve:

It provides sensory innervation to the scalp, cornea, conjunctiva, iris, upper eyelid, lacrimal gland, and the skin and mucus membranes of paranasal sinuses.

It is the branch that is affected in herpes zoster ophthalmicus. After an attack of chickenpox, the virus travels to the trigeminal ganglion and lies dormant there. Reactivation causes typical manifestations such as skin and eyelid involvement, keratitis, uveitis, and conjunctivitis.

Maxillary nerve:

It provides sensory innervation to the lower eyelid, cheeks, maxillary sinus, nasal cavity, lateral nose, upper lip, palate, teeth, gingiva.

Mandibular nerve:

It provides sensory innervation to the dura mater of middle cranial fossa, mucus membranes in the mouth, parts of pinna, tympanic membrane, mylohyoid, anterior belly of digastric and anterior 2/3rds of the tongue.

It also provides exclusive motor innervation to the muscles of mastication, tensor veli palatini, and tensor tympani.

The site marked X is the mandibular foramen which contains the inferior alveolar nerve, a branch of the mandibular nerve. All the muscles mentioned above are supplied by the trunk of mandibular nerve except the lateral pterygoid. The lateral pterygoid is supplied by the anterior

division of mandibular nerve.

In the given case, the medial rectus muscle is paralyzed on the right side. This leads to unopposed action of the lateral rectus, causing the eyeball to move outwards. The medial rectus, inferior rectus and inferior oblique are supplied by the inferior division of the oculomotor nerve (CN III)

Course of the oculomotor nerve:

• The oculomotor nerve arises from the midbrain and emerges, by passing medial to the crus cerebri.
• It passes along the lateral wall of the cavernous sinus and divides into superior and inferior divisions. The two divisions enter the orbit through the superior orbital fissure and innervate the extraocular muscles:
• Superior division - superior rectus and levator palpebrae superioris muscles.
• Inferior division - the inferior rectus, medial rectus, and inferior oblique muscles.

The given scenario is suggestive of injury to the nerve to stapedius which is a branch of the VIIth cranial nerve (facial nerve). During surgery involving the parotid and mandibular region, injury to the facial nerve can damage the nerve to stapedius, hence causing stapedial paralysis which leads to hyperacusis.

The tensor tympani and the stapedius are the muscles of the middle ear and they are innervated by branches of V and VII cranial nerves respectively. Both these muscles contract in response to loud noises and thereby dampen sound. The tensor tympani increases the tension of the tympanic membrane and reduces the force of vibration. Stapedius pulls the stapes posteriorly and reduces the oscillations.

Paralysis of one or both of these muscles causes increased sensitivity to the sounds, a condition known as hyperacusis.

Cavernous sinus thrombosis may lead to the narrowing of the cavernous part of the internal carotid artery (ICA), because the cavernous sinus is closely related to it. The ophthalmic artery will not be involved here, as it is a branch of the cerebral part of the ICA.

Branches of cavernous part of the internal carotid artery:

• Meningeal artery
• Inferior hypophyseal arteries
• Cavernous branch (supplies trigeminal ganglion)

The involvement of the pterygoid canal can injure the vidian nerve, which is formed by:

• Postganglionic sympathetic fibres of the deep petrosal nerve
• Preganglionic parasympathetic fibres of the greater petrosal nerve

Pterygoid canal (Vidian canal):

• The pterygoid canal, also known as the Vidian canal, is a foramen in the base of the skull, located in the pterygoid process of the sphenoid bone, superior to the pterygoid plates, and inferomedial to the foramen rotundum. It transmits the Vidian artery and Vidian nerve from the middle cranial fossa to the pterygopalatine fossa
• It transmits the artery, nerve, and vein of the pterygoid canal (Vidian nerve and Vidian artery)
• into the pterygopalatine fossa.
• The vidian nerve contains the preganglionic fibers of the pterygopalatine ganglion, which provide the secretomotor supply to the nasal mucous glands. Hence vidian neurectomy is indicated in vasomotor rhinitis and intractable rhinnorrhea which is refractory to other treatments.

The given image shows distention of the external jugular vein. Its formative tributaries are the posterior auricular vein and retromandibular vein (posterior division).

Venous drainage of the face and scalp:

The blood from the face and scalp is mainly drained by the facial vein and retromandibular vein.

• The supratrochlear and the supraorbital veins join at the medial angle of the eye to form the angular vein, which continues down as facial vein.
• The superficial temporal vein joins the maxillary vein to form the retromandibular vein. The retromandibular vein divides into anterior and posterior divisions.
• The anterior division of the retromandibular vein joins the facial vein to form the common facial vein, which drains into the internal jugular vein.
• The posterior division of the retromandibular vein joins with the posterior auricular vein to form the external jugular vein. The external jugular vein then drains into the subclavian vein.

The secretomotor fibres from glossopharyngeal nerves relay through the otic ganglion before supplying the parotid gland. Otic ganglion is present medial to the mandibular nerve.

Relations of otic ganglion:

• Superiorly - Foramen ovale
• Laterally - Mandibular nerve
• Medially - Tensor veli palatini
• Posteriorly - Middle meningeal artery

Otic ganglion is a parasympathetic ganglion which supplies secretomotor fibres to the parotid gland and is present below the foramen ovale.

• Preganglionic fibres originate in the inferior salivatory nucleus and pass through the lesser petrosal nerve which is the continuation of the tympanic branch of the glossopharyngeal nerve.
• They relay in the otic ganglion.
• Postganglionic fibres pass by the communicating branches to the auriculotemporal nerve and supply the parotid gland.