The fabella is an accessory ossicle typically found in the lateral head of the gastrocnemius. It occurs in ~20% (range 10-30%) of the population 1.
The fabella can also be fibrocartilaginous in nature and is occasionally found in the medial head of the gastrocnemius. The fabella articulates wi...
Fabry disease is a multisystem disorder which results from an X-linked inborn error of metabolism. The disease is characterised by a deficiency in hydrolase alpha-galactosidase activity with a resultant abnormal accumulation of globotriaosylceramide (Gb3) in various organ systems. In men, the co...
A faceless kidney refers to one in which the normal appearance of the renal sinus on cross-sectional imaging is absent. It was initially described as a sign of duplication of the collecting system 1 (a slice obtained between the two collecting systems will not demonstrate the normal components o...
Facet dislocation refers to anterior displacement of one vertebral body on another. Without a fracture, the only way anterior displacement can occur is by dislocation of the facets.
Facet dislocation can occur to varying degrees:
The injury usua...
The facet (or apophyseal or zygapophyseal) joints are the articulations of the posterior arch of the vertebrae and form part of the posterior column.
They are synovial-lined joints that have a fibrous capsule and connect the articular facets of the vertebrae. The superior facet ...
Facet joint capsules are the fibrous capsule that surround the vertebral facet or zygapophyseal joints. They are particularly thin and loose, attached to the margins of articular facets on adjoining articular processes. The capsules merge medially with the ligamentum flavum.
In the cervical re...
Facet (zygapophyseal) joint injections are one of the most frequently performed spinal interventional procedures, as both treatment for and diagnosis of radicular pain syndrome and facet syndrome. It can be performed under fluoroscopic, or CT image guidance and cervical, thoracic or most commonl...
Facial angiofibroma, also known as fibrous papule, is a fairly common skin lesion seen in males and females after puberty.
They represents a focal vascular and collagen growth.
This lesion is usually solitary and located on the nose skin, measuring 1-5 mm.
There is no hereditary p...
The facial artery is one of the branches of the external carotid artery and supplies blood to the structures of the face.
origin: branch of the external carotid artery a little above the level of the lingual artery
course: ascends anteriorly through the cheek with a tortuous route tow...
The facial bones comprise a set of bones that make up the face:
inferior nasal concha
zygoma (zygomatic bone)
Where these bones join each other, sutures occur.
The facial-cavernous anastomoses are the communications of the facial and deep facial veins with the cavernous sinus.
At the medial canthus of the eye there is a communication with the ophthalmic veins, which drain into the cavernous sinus. Blood from the frontal scalp normally f...
Facial clefts comprise of a wide spectrum of pathologies which result from failure of fusion in the facial region during the embryonic - early fetal period. This results is gap in the fetal face. These clefts can affect the lip, philtrum, alveolus and hard and soft palate to varying degrees.
The facial colliculus is an elevation on the floor of the fourth ventricle and is not formed by the facial nerve nucleus, but by the fibres of the facial nerve arching backwards around the abducens nerve (CN VI) nucleus before turning forwards once more in the caudal pons.
Facial colliculus syndrome refers to a constellation of neurological signs due to a lesion at the facial colliculus, involving:
abducens nerve (CN VI) nucleus
facial nerve (CN VII) fibres at the genu
medial longitudinal fasciculus
lower motor neuron facial nerve palsy ...
Facial fractures are commonly caused by blunt or penetrating trauma sustained during motor vehicle accidents, assaults, and falls. The facial bones are thin and relatively fragile making them susceptible to injury.
Males are affected more commonly than females and facial fractures...
The facial muscles enable facial expression and serve as sphincters and dilators of the orifices of the face. These muscles differ from those of other regions in the body as there is no fascia deep to the skin of the face; many of the facial muscles insert directly into the skin 1.
The facial nerve is one of the key cranial nerves with a complex and broad range of functions.
Although at first glance it is the motor nerve of facial expression which begins as a trunk and emerges from the parotid gland as five branches (see facial nerve branches mnemonic), it has taste and p...
There are many mnemonics to recall the branches of the facial nerve (superior to inferior) as they exit the anterior border of the parotid gland. Examples include:
Tall Zulus Bear Many Children
Two Zulus Bit My Cat
Two Zebras Bit My Coccyx
Ten Zebras Buggered My Car
To Zanzibar By Motor Car...
Facial nerve choristomas are rare, being characterised by non-neoplastic proliferation of smooth muscle cells and fibrous tissue. Facial nerve choristomas presumably can occur anywhere along the course of the facial nerve (CN VII), although the only cases reported are in the internal acoustic me...
Facial nerve schwannoma (FNS), also known as facial nerve neuroma/neurilemoma, is a schwannoma that arises from the facial nerve. They are generally uncommon, and when involving the temporal bone, make up less than 1% of all temporal bone tumours.
FNS is a rare tumour 2.
Helpful mnemonics for remembering the segments of the facial nerve include:
I Love Going To Makeover Parties 1
I Love Grinning, Then Making Pouts
both grinning and pouting are performed by muscles which are innervated by the facial nerve
I Must Learn To Make (facial) Expressions
Facial palsy refers to the neurological syndrome of facial paralysis. It can result from a broad range of physiological insults to the facial nerve or its central nervous system origins. The most common causes of this is Bell palsy.
While facial palsy refers to the clinical presen...
The facial vein (previously known as the anterior facial vein) is the continuation of the angular vein and joins the anterior branch of the retromandibular vein to form the common facial vein 1-3.
At the level of the lower margin of the orbit, the angular vein becomes the facial ...
Factitious hyperthyroidism or thyrotoxicosis factitia refers to precipitation of thyrotoxicosis due to exogenous ingestion of thyroid hormone (e.g. levothyroxine). It has been rarely associated with myocardial ischaemia 2.
The hypervascularity which is seen wi...
A faecaloma is a mass of faeces most frequently noted in the rectum and sigmoid colon, that is much harder than a faecal impaction due to coprostasis.
Usually, the faecal matter accumulates in the intestine, then stagnates and increases in volume until the intestine becomes deformed ...
Fahr syndrome, also known as bilateral striatopallidodentate calcinosis, is characterised by abnormal vascular calcium deposition, particularly in the basal ganglia, cerebellar dentate nuclei, and white matter, with subsequent atrophy.
It can be either primary (usually autosomal dominant) or se...
Failed back syndrome refers to persistent leg and/or lumbar back pain after a surgical procedure. The pathophysiology of this syndrome is complex, as often the operation was technically successful.
Other names for failed back syndrome include failed back surgery syndrome, post-lam...
Failed early pregnancy refers to the death of the embryo and therefore, miscarriage. The most common cause of embryonic death is a chromosomal abnormality.
Findings diagnostic of pregnancy failure
crown-rump length (CRL) of ≥7 mm and no heartbeat on a transva...
Failed pregnancy is a pregnancy that will not carry through to term.
It is termed a miscarriage or failed early pregnancy when fetal demise occurs before 20 weeks gestational age and fetal death in utero (FDIU) when it occurs after 20 weeks gestation.
The term "non-viable" pr...
The falciform crescent (or crista falciformis) is a horizontal ridge that divides the internal acoustic meatus into superior and inferior portions.
The facial nerve and superior vestibular nerve (SVN) travel in the superior portion of the IAM with the facial nerve anterior to the SVN ...
The falciform ligament is a broad and thin peritoneal ligament. It is sickle-shaped (Latin: "falciform") and a remnant of the ventral mesentery of the fetus.
It is situated in an anteroposterior plane, but lies obliquely so that one surface faces forward and is in contact with the peritoneum be...
The falciform ligament sign (also called the Silver sign) is a sign seen with a pneumoperitoneum.
It is almost never seen in isolation. If there is enough free gas to outline the falciform ligament, there is usually enough gas to also provide at least a Rigler sign.
The falciform ligament con...
The fallen fragment sign refers to the presence of a bone fracture fragment resting dependently in a cystic bone lesion. This finding is said to be pathognomonic for a simple (unicameral) bone cyst following a pathological fracture. Although it has occasionally been reported with other cystic le...
The fallen lung sign (also known as CT fallen lung sign) describes the appearance of collapsed lung away from the mediastinum encountered with tracheobronchial injury (in particular those >2 cm away from the carina). It is helpful to look for this rare but specific sign, in cases of unexplained ...
Fall onto an outstretched hand (FOOSH) is a common mechanism for wrist-forearm fractures, in certain cases with involvement of elbow structures, particularly in children.
Some injuries that result from such a fall include:
The Fallopian (facial) canal refers to a bony canal through which the facial nerve traverses the petrous temporal bone, from the internal acoustic meatus to the stylomastoid foramen.
It is, for those of you fond of trivia, the longest bony canal through which a nerve passes. It is also responsi...
Fallopian tube rupture is most often a complication of a tubal ectopic pregnancy where the pregnancy breaks open due to progressive growth. It can potentially lead to shock.
Factors that raise the risk for a tubal rupture in a given tubal ectopic pregnancy include 2-4:
A Fallopian tube polyp refers to a small focal lesion of ectopic endometrial tissue located at the intramural portion of the fallopian tube.
The reported incidence is 1- 2.5% on hysterosalpingograms performed for assessment of infertility 3
Most patients w...
Fallopian tube spasm is a transient functional anomaly that can mimic a true mechanical tubal occlusion. At radiography, tubal spasm cannot be distinguished from a tubal occlusion. Administration of spasmolytic agents such as Glucagon can occasionally result in uterine muscle relaxation and cons...
Fallopian tube torsion is a type of adnexal torsion and usually occurs in association with an ovarian torsion (when it is then termed a tubo-ovarian torsion). An isolated fallopian tube torsion is rare but can occur.
An isolated tubal torsion can occur as a late complication of tuba...
False aneurysms, also known as a pseudoaneurysm, is when there is a breach in the vessel wall such that blood leaks through the wall but is contained by the adventitia or surrounding perivascular soft tissue. A direct communication of blood flow exists between the vessel lumen and the aneurysm l...
False umbilical cord knots are commonly formed variants in the umbilical cord anatomy. It basically represents, exaggerated looping of the umbilical cord vessels, causing focal dilatation of the umbilical cord vessels.
bulge or protruberance in the umbilical c...
The false vocal cords (vestibular folds, ventricular folds) are paired shelf-like structures located within the supraglottic larynx that divide the vestibule above from the ventricle below.
The vestibular ligaments are the ligamentous component of the false vocal cords and const...
The falx cerebelli is a small infolding of the dura in the sagittal plane over the floor of the posterior cranial fossa. It partially separates the two cerebellar hemispheres 1.
The falx cerebelli is attached posteriorly in the midline to the internal occipital crest of the occip...
The falx cerebri is the largest of the four main folds (or septa) of the intracranial dura mater, separating the cerebral hemispheres 1.
The falx cerebri is a double-fold of dura mater that descends through the interhemispheric fissure in the midline of the brain to separate the...
In discussing mineralisation of the falx cerebri, many radiology textbooks use the term falx calcification and make no mention of falx ossification.
Ossification of dural folds is relatively unusual; one study suggested a prevalence of falx ossification of 0.7% 1. Even though, os...
Familial adenomatous polyposis syndrome (FAPS) is characterised by the presence of hundreds of adenomatous polyps in the colon. It is the most common of the polyposis syndromes.
Familial polyposis coli, attenuated familial adenomatous polyposis and Gardner syndrome are all variants...
Familial multiple cavernous malformation syndrome(s) are uncommon, accounting for only a minority of cavernous malformations.
It has been more frequently reported in patients of Hispanic descent 1.
The presentation is most commonly with seizures (38-55%) 1 ...
Familial multiple lipomatosis (FML) is a hereditary syndrome of multiple encapsulated lipomas which are found on the trunk and extremities, with relative sparing of the head and shoulders.
It is clinically distinct from the similarly named multiple symmetric lipomatosis with which it is freque...
Fanconi anaemia (FA) is a rare disorder characterised by progressive bone marrow failure, various congenital abnormalities, and predisposition to malignancies (often acute myeloid leukaemia). It is considered the commonest type of inherited marrow failure syndrome 7.
The fascial tail sign is the linear extension along the fascia/muscular aponeurosis from a deeper tumour.
It appears as a tail and is best appreciated on MRI, classically seen in desmoid tumours as T2 hypointense bands that progressively enhance particularly on delayed ph...
Fascicular sign is a finding on T2-weighted MRI images that suggests a lesion of neurogenic origin. It is characterised by multiple small ring-like structures with peripheral hyperintensity representing the fascicular bundles within the nerves.
It is found in various neurogenic tumours, includi...
Fatal familial insomnia is an extremely rare autosomally inherited prion disease 1. Unlike other prion diseases, it does not exhibit spongiform changes. The main pathological findings are gliosis in the inferior olivary nuclei and thalami.
Fat containing breast lesions generally have some radiolucent component on mammography.
They are generally classified at BIRADS II lesions.
fat necrosis within the breast/oil cyst
intramammary lymph node: classically has a central fatty hilu...
A variety of benign and malignant liver lesions may contain macroscopic and/or intracytoplasmic fat in sufficient quantities enabling characterization on imaging studies. Most fat containing liver lesions (80%) in patients with cirrhosis are malignant, most of which are hepatocellular carcinoma ...
There are numerous fat containing renal lesions, including:
renal cell carcinoma
renal or perirenal lipoma
Non-mass lesions may also occasionally contain fat:
renal junction line
fat in a renal scar
renal sinus lipomatosis
The differential of a fat containing solitary pulmonary nodule is very narrow.
In a well circumscribed smooth or lobulated mass (especially if it has been largely stable in size over time) presence of fat is essentially pathognomonic of a pulmonary hamartoma, and usually not further assessment ...
There is a long list of fat containing thoracic lesions. They may involve the mediastinum, lung, pleura or chest wall.
Differential diagnosis includes:
intrapulmonary: fat containing pulmonary lesions
Fatco syndrome is a syndrome consisting of
tibial campomelia and
It is a syndrome of unknown genetic basis and inheritance with variable expressivity and penetrance.
Fuhrmann syndrome and Al-Awadi syndrome are said to be similar to FA...
Fat embolism syndrome (FES) is a rare clinical condition caused by circulating fat emboli leading to a multisystemic dysfunction. The classical clinical triad consists of:
It occurs in ~2.5% (range 0.5-4%) of th...
The fat halo sign refers to a feature seen on CT examination of the abdomen, and represents infiltration of the submucosa with fat, between the muscularis propria and the mucosa. It is characterised by an inner (mucosa) and outer (muscularis propria and serosa) ring of enhancing bowel wall along...
Fatigue fractures are a type of stress fracture due to abnormal stresses on normal bone. They should not be confused with an insufficiency fracture, which occurs due to normal stresses on abnormal bone. Plain films typically demonstrate a linear sclerotic region. MRI is the most sensitive and sp...
Fat necrosis within the breast is a pathological process that occurs when there is saponification of local fat. It is a benign inflammatory process and is becoming increasingly common with the greater use of breast conserving surgery and mammoplasty procedures.
Most at risk are mi...
In fat-pad impingement syndromes the aetiologies are different for each knee fat pad.
In anterior suprapatellar fat pad impingment syndrome the cause is usually due to either a developmental cause related to the anatomy of the extensor mechanism, or may be related to abnormal mechanics. In this...
The fat redistribution syndrome (or HIV lipodystrophy syndrome) is seen in a number of AIDS patients on HAART. It is characterised by typical changes in body fat distribution.
Features include :
hypertrophy in the neck fat pad (buffalo hump)
increased fat in the abdominal region (protease pau...
The fat ring sign (also known as a fat halo sign) describes preservation of fat around the mesenteric vessels and around soft tissue nodules on a background of diffuse fat stranding in patients with mesenteric panniculitis or mesenteric lipomas.
This finding may help distinguish mesenteric pan...
Fat stranding is a common sign on CT seen anywhere fat can be found but is most commonly seen in the abdomen/pelvis, but also in the retroperitoneum, thorax and subcutaneous tissues. It can be helpful in localising both acute and chronic pathology.
Fat stranding can a...
Fat stranding is a sign that is seen on CT. It describes the change in attenuation of fat around an inflamed structure and is a very helpful signpost for intra-abdominal pathology.
This is a summary article; read more in our article on fat stranding on CT.
Fat suppression is commonly used in magnetic resonance (MR) imaging to suppress the signal from adipose tissue or detect adipose tissue 1. It can be applied to both T1 and T2 weighted sequences.
Due to short relaxation times, fat has a high signal on magnetic resonance images (MRI). This high ...
A fatty falx cerebri is a common finding, seen (according to one study) 7.3% of patients, and is explained by fat being a normal feature of the extradural neural axis compartment located between the two visceral layers of the falx.
A fatty falx is an incidental finding and should not be mistak...
Fatty mediastinal masses are relatively uncommon, and the differential diagnosis is brief, including 1-4:
benign mature teratoma
extravasation of lipid-rich hyperalimentation fluid 3
fibrofatty replacement of the central portion of mediastinal l...
Fatty nodal metaplasia in the neck occurs as a result of chronic inflammation or radiotherapy 3. The normal fatty nodal hilum enlarges, such that the lymph node appears cystic. However, its center is of fatty density. There is no surrounding stranding, and the node otherwise looks normal.
Faulty fetal packing, also known as congenital vault depression, is a congenital concave depression of the skull in a newborn.
Occurs in 1 in 10,000 births 1.
This appearance is due to external compression on the skull from 1,2:
fetal limb or twin
The Fazekas scale is used to simply quantify the amount of white matter T2 hyperintense lesions usually attributed to chronic small vessel ischaemia, although clearly not all such lesions are due to this.
This classification was proposed by Fazekas et al. in 1987 1 and at the time of writing (l...
The FBI sign is an acronym referring to the components that form a lipohaemarthrosis. It stands for:
FCD may refer to:
focal cortical dysplasia (of the brain)
fibrous cortical defect (of the bone)
The radiographic features of a Charcot joint can be remembered by using the following mnemonic:
6 Ds of Charcot joint
increased Density (subchondral sclerosis)
Debris (intra-articular loose bodies)
The causes of Charcot arthrop...
Febrile infection-related epilepsy syndrome (FIRES) is a severe postinfectious neurological disorder that presents with status epilepticus in a previously normal child (or less commonly adult) after a febrile illness.
FIRES has received several names in the literature:
Feeding vessel sign consists of a distinct vessel leading directly to a nodule or a mass. This sign indicates either that the lesion has a haematogenous origin or that the disease process occurs near small pulmonary vessels.
A number of vessel-related non-neoplastic disorders of the lung produ...
Feingold syndrome is characterised by the combination of:
alimentary tract atresias especially oesophageal atresia
Feline oesophagus also known as oesophageal shiver, refers to the transient transverse bands seen in the mid and lower oesophagus on a double contrast barium swallow.
The appearance is almost always associated with active gastro-oesophageal reflux 2,3 and is thought to be due to contraction of ...
Felty syndrome comprises of the combination of:
rheumatoid arthritis (RA)
It is thought to occur in ~ 1% of patients with rheumatoid arthritis 2.
rheumatoid factor (RF): Over 95% of FS patients are positive 5
Female infertility is common, and can be due to a number of factors. Radiology often plays a key part of the work-up.
Often more than one factor (including male infertility) is the cause of infertility, some of the common causes are listed below 1-3:
age > 35 years
Female prostate sign is a characteristic imaging sign seen in patients with a large urethral diverticulum.
A large urethral diverticulum in females surrounds the urethra, and elevates the base of the bladder, mimicking the typical appearance of enlarged prostate in males.
Female pseudohermaphroditism (FPH) is a form of disorder of gender development.
Patients with female pseudohermaphroditism have female internal genitalia and female karyotype (XX) with various degree of external genitalia virilization.
congenital adrenal hyperplasia (CAH) ...
The female reproductive system (or tract) comprises of the vagina, uterus, uterine tubes and ovaries.
It can be imaged using almost the entire range of modalities but ultrasound and MRI are most useful.
The female urethra is a simple tube that extends from the internal urethral orifice of the bladder to the external urethral orifice in the vestibule of the vagina.
The female urethra measures approximately 4 cm in length. It is embedded in the anterior vaginal wall and runs with...
Femoral anteversion refers to the orientation of the femoral neck in relation to the femoral condyles at the level of the knee. In most cases, the femoral neck is oriented anteriorly as compared to the femoral condyles. In the case of posterior orientation, the term femoral retroversion is also ...
Femoral artery pseudoaneurysms are usually iatrogenic as the femoral artery is the vessel of choice for most endovascular arterial interventions.
inadequate compression following endovascular intervention
improper arterial puncture tec...
The femoral canal, or the medial compartment of the femoral sheath, is the inverted cone-shaped fascial space medial to the femoral vein within the upper femoral triangle. It is only 1-2 cm long and opens superiorly as the femoral ring. It serves two purposes:
allows the femoral vein to expand ...
A femoral hernia is a type of groin herniation and comprises of a protrusion of a peritoneal sac through the femoral ring into the femoral canal, posterior and inferior to the inguinal ligament. The sac may contain preperitoneal fat, omentum, small bowel, or other structures.
Neck of femur fractures (NOF) are common injuries sustained by older patients who are both more likely to have unsteadiness of gait and reduced bone mineral density, predisposing to fracture. Elderly osteoporotic women are at greatest risk.
It is anticipated that the total number ...
The femoral nerve is a large nerve arising from the lumbar plexus and one of two major nerves supplying the lower limb.
It arises from posterior divisions of L2-L4 roots of the lumbar plexus.
emerges from the lateral border of the psoas muscle to descend between ...