I-131 (or 131I) is a radioisotope used in the diagnosis and treatment of thyroid lesions. It is one of the oldest radiotracers used in nuclear medicine, in use for over 50 years. It is predominately used in thyroid ablation therapy, for patients post thyroidectomy, and for metastatic thyroid ca...
The ice cream cone sign may refer to:
the appearance of the head of malleus and the body and short process of the incus on axial CT scan: failure of this normal configuration suggests incudomalleolar dysarticulation
the ball of the ice cream is formed by the head of malleus and cone is formed ...
IgG4-related disease (IgG4-RD) is a systemic disease that is characterised by extensive IgG4-positive plasma cells and T-lymphocyte infiltration of various organs.
This condition has been known by many other names in the past, such as IgG4-related sclerosing disease, IgG4-related s...
The maxillary incisive canal runs through the maxilla in the midline. It connects the inferior nasal cavity with the superior oral cavity, opening at the incisive foramen posterior to the central maxillary incisor teeth. It contains the descending palatine artery and the nasopalatine nerve.
Incisive canal cysts, also known as nasopalatine duct cysts (NPDC), are developmental, non-neoplastic cysts arising from degeneration of nasopalatine ducts. These ducts usually regress in fetal life. The persistence of ductal epithelium leads to formation of cyst.
It is considered the most comm...
The incisive foramen (also known as nasopalatine foramen or anterior palatine foramen) is the oral opening of the nasopalatine canal. It is located in the maxilla in the incisive fossa, midline in the palate posterior to the central incisors, at the junction of the medial palatine and incisive s...
The incisive nerve is one of the two terminal branches of the inferior alveolar nerve, a branch of the posterior division of the mandibular division of the trigeminal nerve. It continues running anteriorly in the medullary cavity of the mandible after the mental nerve branches off and exits via ...
The incus is the middle of the ossicles articulating with the head of the malleus anteromedially and the stapes inferomedially.
a body which articulates with the head of the malleus, and to which the superior ligament of the incus is attached (to the roof of the middle ear cavit...
Infantile cervical ligament oedema can typically be seen when infants have suffered accidental or abusive head and neck trauma. The finding is best seen on sagittal STIR images.
The posterior ligamentous complex refers to the ligamentum flavum and interspinous ligaments. The anteri...
The inferior alveolar artery is a branch of the maxillary artery. It runs with the inferior alveolar nerve as it descends through the infratemporal fossa and enters the mandibular canal and supplies mandibular teeth. In the region of the first premolar it bifurcates into the incisive and mental ...
The inferior alveolar nerve or inferior dental nerve is a mixed sensory and motor branch of the posterior division of the mandibular division of the trigeminal nerve in the pterogomandibular space of the oral cavity.
The inferior alveolar nerve divides off the posterior division ...
Inferior labial artery (old name: inferior coronary artery) is one of the facial branches of the facial artery. It is smaller than the superior labial artery. It supplies the lower lip, including its labial glands, mucous membranes and muscles.
origin: facial branch of the facial arter...
The inferior longitudinal muscle of the tongue is one of the 4 intrinsic muscles of the tongue which alters the shape of the tongue mass, being entirely confined to the tongue without an attachment outside the tongue (like the extrinsic muscles of the tongue).
The muscles fibres ...
The inferior median clival canal also known as the canalis basilaris medianus is a rare anatomical variant of the clivus, which passes in the sagittal plane from the intracranial surface of the clivus to its retropharyngeal surface. It is generally thought to represent a remnant of the notocord....
The inferior nasal concha is one of the conchae in the nose. It extends horizontally along the lateral wall of the nasal cavity and consists of a lamina of spongy bone, curled upon itself like a scroll. Each inferior nasal concha is considered a facial pair of bones since they arise from the max...
The inferior oblique muscle is one of six extra-ocular muscles that control eye movements.
innervation: inferior branch of the oculomotor nerve (CN III)
origin: orbital surface of the maxilla
insertion: globe (posterior, inferolateral surface)
primary function: one of two ocular ext...
The inferior ophthalmic vein (IOV) is a vein of the inferior orbit and is smaller than the more well known superior ophthalmic vein.
The vein forms at the confluence of several veins within the anteroinferior orbit along the infraorbital margin from facial vein tributaries. It co...
The inferior pharyngeal constrictor muscle is one of the pharyngeal constrictor muscles. Its primary action is constriction of the pharynx (in coordination with the superior pharyngeal constrictor and the middle pharyngeal constrictor muscles) to deliver a bolus of food into the oesophagus.
The inferior rectus muscles is one of the 6 extra-ocular muscles that control eye movements.
innervation: inferior branch of the oculomotor nerve (CN III)
origin: Annulus of Zinn (tendinous ring)
insertion: globe (anterior, inferior surface)
primary function: one of two ocular depre...
The inferior thyroid artery is a branch of the thyrocervical trunk (85%) or subclavian artery (15%) and ascends to enter the thyroid gland on its posterior surface, as well as supplying both the superior and inferior parathyroid glands 1. The nerve is closely related to the ascending limb of the...
The infrahyoid muscles or strap muscles are a group of four paired muscles in the anterior neck below the hyoid bone, within the muscular triangle. They are responsible for depressing the hyoid during swallowing.
The four muscles are:
sternohyoid: superficial and medial
omohyoid: superficial ...
The infraorbital artery is a branch of the third part of the maxillary artery. It runs through the inferior orbital fissure, orbit, infraorbital canal then the infraorbital foramen. Here it gives off the anterior superior alveolar artery which supplies the anterior teeth and the anterior part of...
The infraorbital foramen is located in the maxillary bone. It is the anterior opening of the infraorbital canal, which is the anterior continuation of the infraorbital groove, which course through the floor of the orbit. The canal may reside entirely in the maxillary sinus, suspended from the si...
The infraorbital nerve is a branch of the maxillary division of the trigeminal nerve.
The infraorbital nerve divides off the maxillary division just after emerging from the foramen rotundum to enter the pterygopalatine fossa. It courses laterally over the palatine bone and maxi...
The infratemporal fossa is a complex space that lies posterolateral to the maxillary sinus and many important nerves and vessels traverse it.
The infratemporal fossa is the space between the skull base, lateral pharyngeal wall and the ramus of mandible. The fossa communicates w...
The infratrochlear nerve is an extraconal branch of the nasociliary nerve, a branch of ophthalmic division of the trigeminal nerve. Some authors describe it as the terminal branch of the nasociliary nerve. It courses through the medial aspect of the extraconal space of the orbit inferior to the ...
Ingested bones that become lodged in the throat or gastrointestinal tract are a common presentation to the emergency department. Recognition is important because these cases can be potentially fatal.
Patients may present with a 'foreign body' feeling in the throat after eating fish ...
The inion is the tip of external occipital protuberance, the midline bony prominance in the occipital bone where the ligamentum nuchae and trapezius muscle attaches. It is usually easily palpable.
It is the the surface marking of the internal attachment of the tentorium cerebelli.
It is one of...
The inner ear refers to the bony labyrinth and its contents and the membranous labyrinth. It is divided into three sections:
A useful mnemonic to remember innervation of the muscles of the middle ear is:
S for Stapedius
T for Tensor Tympani
S: stapedius is supplied by a branch of the facial nerve - the Seventh cranial nerve. It is also the Smallest muscle in the body, and inserts onto the neck of Stapes.
Inspissated colloid (colloid crystals) in a thyroid nodule leads to focal hyperechogenic foci, which can potentially be confused with microcalcifications.
hyperechoic focus in a thyroid nodule
reverberation artifact / comet-tail artifact
this feature is the most reliabl...
Internal auditory canal (IAC) diverticulum are small focal outpouching arising from the anterolateral wall of the IAC.
In one study, they were identified in 5% of petrous temporal bone CT-scan 1. In the same study, it was coexisting with otosclerosis in 1% of cases 1.
A mnemonic to remember the relative position of nerves inside the internal auditory canal (IAC) is:
Seven up, Coke down
Four nerves pass through the IAC:
facial nerve (CN VII)
three components of the vestibulocochlear nerve (CN VIII)
cochlear nerve (CN VIIIc)
superior vestibular n...
The internal jugular vein (IJV) is the major venous return from the brain, upper face and neck.
Origin and course
It is formed by the union of inferior petrosal and sigmoid dural venous sinuses in or just distal to the jugular foramen (forming the jugular bulb). It descends in t...
A useful mnemonic to remember the branches of the internal jugular vein is:
Medical Schools Let Fun People In
From inferior to superior:
M: middle thyroid vein
S: superior thyroid vein
L: lingual vein
F: facial vein
P: pharyngeal vein
I: inferior petrosal sinus
The internasal suture is a single, midline cranial suture between the two nasal bones. It meets the frontonasal suture to form the nasion 1.
The interscalar septum is a thin bony plate that separates each turns of the cochlea 1.
It radiates from the modiolus laterally to the spiral ligament 2. Vessels (venules, arterioles and capillaries) run within the septum through bony canals 2.
Partial absence of the intersc...
The intraconal orbital compartment or intraconal space is the conical space within the orbit and musculofascial cone, the base of which is anterior and is formed by the posterior half of the globe. The sides are formed by the extraocular muscles and their surrounding fascia which pass posteriorl...
Intraconal orbital lesions are broadly divided into two main groups; those with or without involvement of the optic nerves:
Lesions with optic nerve involvement:
optic nerve glioma
optic nerve meningioma
lymphoma and leukaemia
Intracranial dermoid cysts are uncommon lesions with characteristic imaging appearances. They can be thought of as along the spectrum: from epidermoid cysts at one end (containing only desquamated squamous epithelium) and teratomas at the other (containing essentially any kind of tissue from all...
Intraductal papilloma of salivary gland (also known as an inverted ductal papilloma or sialadenoma papilliferum) is a benign relatively rare salivary gland tumour. '
They typically arise in adulthood and there may be a slight male predilection.
They may show a characte...
Intraosseous meningioma, also referred as primary intraosseous meningioma, is a rare subtype of meningioma that accounts for less than 1% of all osseous tumours. They fall under the subgroup of primary extradural meningiomas.
It is important to note that it has been argued by some ...
The intrinsic muscles of the larynx can be considered in two groups:
muscles that control the inlet of the larynx
muscles that move the vocal ligaments
Muscles of the inlet
aryepiglottic muscle: lies within the aryepiglottic fold, runs from the side of the epiglottis and inser...
The intrinsic muscles of the tongue are a group of 4 muscular bands in the tongue. In comparison to the extrinsic muscles of the tongue, they are entirely within the tongue with no external attachments. They act to alter the shape of the tongue where as the extrinsic tongue muscles alter the pos...
Inverted papillomas are a type of Schneiderian papilloma. They are uncommon with distinctive pathological and imaging features.
The term inverted papilloma is also used to describe a urothelial lesion. For a discussion of that entity, please refer to inverted papilloma of the urin...
Iodine123 (I123) is a radioisotope of the element iodine (atomic number 53) used in nuclear medicine imaging including to scan the thyroid gland.
Uses, dosages, and time of Imaging
routine scan: 100-400 microCi po, image at 4-6 or 24 hours
thyroid cancer scan: 1.5 mCi po, image at 4-6 or 24 ...
An isolated cleft palate is a type of facial cleft. This is a much rarer occurrence than a cleft lip +/- palate and is thought to represent a different pathological entity.
The estimated incidence is at ~1 per 2000-2500 pregnancies 4-5. There may be a slight female predilection 4....