The parasellar dark T2 signal sign is a MRI feature where there is parasellar low T2 signal. Some authors describe is as a specific finding in differentiating lymphocytic hypophysitis from a pituitary adenoma.
Optic disc edema refers to unilateral or bilateral swelling of the optic disc.
Optic disc edema describes the swelling of nerve fiber layer at the optic nerve head, and it is the consequence of many different pathological processes. Optic disc edema is sometimes mistaken for papi...
Radiation therapy has the potential to cause complications in many organ systems, many of which, especially in the thorax, are important for radiologists to be aware of.
acute radiation syndrome
complications of cranial radiation therapy
radiation-induced cerebral vasculopathy
The paracingulate sulcus is a secondary sulcus running anteroposteriorly in the medial surface of the frontal lobe above and parallel to the cingulate sulcus 1. It is only found in the great apes and only identified in 70-89% of humans 1.
Tetanus is a rare vaccine-preventable disease caused by Clostridium tetani, a ubiquitous soil bacterium which contaminates open wounds. It secretes a powerful neurotoxin which degrades neuromuscular junction function, producing muscle spasms and, despite intensive intervention, is often fatal.
The notch sign refers to abnormally deep depression at the tumor margin in contrast-enhanced MRI in primary CNS lymphoma 1. It is not an uncommon sign in primary CNS lymphoma and can be seen in both immunocompetent and immunocompromised patients. It suggests an irregular growth pattern as well a...
Non-arteritic anterior ischemic optic neuropathy (NAION) is a form of ischemic optic neuropathy.
It is considered the most common acute optic neuropathy in patients over 50 years of age (especially in those with vasculopathy risk factors (e.g. diabetes mellitus, hypertension, and ...
Area postrema syndrome is a disorder of the chemoreceptor trigger zone (area postrema) which is located on the medial posteroinferior surface of the medulla oblongata. It is usually a demyelinating disorder, as one of the core clinical characteristics of neuromyelitis optica spectrum disorder 1,...
Arhinencephaly, sometimes spelled arrhinencephaly, refers to congenital absence of the olfactory bulbs and tracts. It causes congenital anosmia and can be found in:
CT angiography of the circle of Willis (CTA COW) is a technique that allows visualization of the intracranial arteries; specifically the circle of Willis. While digital subtraction angiography (DSA) remains the gold standard for the diagnosis of intracranial aneurysms especially, CTA is a less i...
Hypoglossal nerve palsies, or twelfth nerve palsies, result in weakness of the muscles supplied by the hypoglossal nerve, namely the intrinsic and extrinsic tongue muscles, except for palatoglossus.
The hypoglossal nucleus receives a major component of contralateral corti...
The sphincter pupillae muscle is a circular ring of smooth muscle within the iris responsible for constriction of the pupil (miosis). The structure is stimulated by the parasympathetic nervous system causing the muscle to decrease in diameter as it contracts.
The sphincter pupill...
A persistent primitive olfactory artery (PPOA) is a rare variant of the proximal anterior cerebral artery 1,2. It is proposed to be more prone to aneurysms due to its sharp hairpin-like turn. Embryologically, the persistent primitive olfactory artery is the rostral division of the primitive inte...
Clival fractures are uncommon skull base fractures resulting from high-energy cranial trauma and are usually associated with other skull vault fractures and brain injuries.
For a general discussion, please refer to the article on basilar fractures of the skull.
Most fractures of ...
An intracochlear schwannoma is a subtype of an intralabyrinthine schwannoma which is a schwannoma arising in relation to the 8th cranial nerve.
Patients may present with unilateral sensorineural hearing loss.
Schwannomas that are confined exclusively to the c...
Dragonfly sign describes the appearance of the cerebellum on coronal images, which is seen secondary to cerebellar atrophy in pontocerebellar hypoplasia 1.
The sign is so called as the whole cerebellum resembles the shape of a dragonfly if one imagines the vermis is the body of the insect and t...
Atypical neurofibromas and atypical neurofibromatous neoplasms of uncertain biologic potential (collectively AN/ANNUBP) refer to neurofibromas with atypical histological features. They are considered premalignant with an increased risk of progressing to a malignant peripheral nerve sheath tumor....
Alpha-fetoprotein (AFP) in the cerebrospinal spinal fluid (CSF) has been reported as a tumor marker for some intracranial tumors with yolk sac elements, and teratoma 1.
intracranial yolk sac tumor
intracranial embryonal carcinoma
congenital CNS tumors with yolk sac ...
The Brain and Spinal Injury Center (BASIC) score is a classification system for grading acute traumatic spinal cord injury based on the axial extent of intramedullary signal abnormality on T2 weighted MRI.
The BASIC score is an ordinal scale that is graded 0 to 4 1:
BASIC 0 (no...
Intracranial yolk sac tumors represent 2% of nongerminomatous germ cell tumors 1.
Intracranial yolk sac tumors commonly occur in childhood or adolescence. CSF alfa fetoprotein can act as a tumor marker for yolk sac tumors.
Intracranial yolk sac tumors are...
Suspected physical abuse, also known as non-accidental injury (NAI), can result in a range of head injuries.
Infants have a relatively large head size as compared to their body mass, weak neck muscles, large subarachnoid space, relatively flat skull base and pliable, thin skull. The ...
Infant-type hemispheric gliomas, also known as infant high-grade gliomas, are high-grade brain tumors occurring in children.
Infant-type hemispheric gliomas belong to the family of "pediatric high-grade diffuse gliomas" of the 2021 WHO Classification of Tumors of the Central Nervou...
Diffuse pediatric-type high-grade gliomas, H3-wildtype and IDH-wildtype are high-grade pediatric tumors recently included in the 5th Edition (2021) of the WHO brain tumor classification.
Diffuse pediatric-type high-grade gliomas H3-wildtype and IDH-wildtype are classified among the...
Posterior fossa ependymomas are the most common type of ependymoma, most commonly occurring in children. They are divided on the basis of DNA-methylation profiling into two groups, A and B.
Posterior fossa ependymomas are encountered in all age groups but are usually encountered ...
Diffuse hemispheric gliomas, H3 G34 mutant are rare and high grade infiltrating tumors typically presenting in adolescents and young adults.
Diffuse hemispheric gliomas H3 G34 mutant have been recently included in the 5th Edition (2021) of the WHO brain tumor classification 1 among...
Medulloepitheliomas of the optic disc and optic nerve are extremely rare primary intraocular embryonal tumors arising from the optic disc and optic nerve.
A medulloepithelioma of the optic disc and optic nerve may also be referred to as a diktyoma or teratoneuroma, although the use...
Reye syndrome is a rare pediatric condition characterized by acute onset encephalopathy, severe vomiting and fatty liver failure. It typically presents in children recovering from a viral illness, most commonly influenza or chickenpox 1.
Reye syndrome is usually seen between the ...
Cacosmia refers to a form of olfactory dysfunction where the patient has an inability to "recognize" smells. It can arise from a number of pathologies and can include peripheral sinonasal and central sensorineural components. In this situation, the patient knows there is a smell but cannot disti...
Medulloepitheliomas of the brain are rare, highly malignant, primitive embryonic tumors derived from the primitive medullary plate and neural tube. These tumors, once considered distinct entities, are now thought to be a pattern of embryonal tumors with multilayered rosettes. Please refer to tha...
The suboccipital cavernous sinuses are paired venous plexuses that surround the horizontal (distal V3) portion of the vertebral arteries at the craniocervical junction. Its name derives from its resemblance to the cavernous sinus as it is a venous cushion surrounding a large arterial loop at the...
Central nervous system neuroblastoma, FOXR2-activated is a novel brain tumor entity recently included in the WHO brain tumor classification 1.
Central nervous system neuroblastoma with FOXR2 activation was identified in 2016 as a new molecular entity, distinguished from primitive n...
Dural venous sinus cysts are rare, usually congenital lesions, most commonly observed as fluid-filled intraluminal lesions on cross-sectional imaging.
Dural venous sinus cysts are very rare, and are mostly congenital 1.
Most dural venous sinus cysts are true fluid-fi...
Acute leukoencephalopathy with restricted diffusion (ALERD) is a clinicoradiological spectrum of disease with clinical features of leukoencephalopathy and associated imaging findings where diffusion restriction is the dominant finding.
The dominant radiological feature is...
The flame sign refers to a gradual tapering of contrast opacification in the mid-cervical internal carotid artery, sparing the carotid bulb. The sign can be observed on angiography (digital subtraction angiography 1, CT angiography 1, or contrast-enhanced MR angiography 2) in either of two scena...
Subependymal cysts may either be postnatally acquired posthemorrhagic cysts or may be congenital (germinolytic). The congenital cysts may result from infection, ischemic injury, or hemorrhage.
Most frequently seen in preterm infants, likely related to their persistent germinal mat...
The Heidelberg bleeding classification categorizes intracranial hemorrhages occurring after ischemic stroke and reperfusion therapy.
Class 1: hemorrhagic transformation of infarcted brain tissue
1a: HI1: scattered small petechiae, no mass effect
1b: HI2: confluent petech...
Diffuse low-grade glioma, MAPK pathway-altered is a novel tumor type included in the 5th Edition (2021) of the WHO brain tumor classification 1.
Several genetic mutations were recognized in low-grade IDH-wt/H3-wt brain diffuse gliomas occurring in children and adolescents, such as ...
Salt and pepper noise, also known as impulse noise, has been used to describe the characteristic appearance of a certain artifact seen on MRI.
The artifact looks like innumerable black and white pixels throughout the image. Smoothing filters are algorithms designed to diminish the noise whilst ...
Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is an epileptogenic tumor of children and young adults.
First described in 2016 1, polymorphous low-grade neuroepithelial tumor of the young has been recently included in the new family of "pediatric-type" low-grade ...
The autonomic nervous system (ANS) is a subdivision of the peripheral nervous system. The autonomic system provides innervation of the involuntary muscles, i.e. myocardium and smooth muscle, and glands, through which fine control of homeostasis is maintained.
The afferent innervation of the aut...
The peripheral nervous system (PNS) consists of the nerves (cranial nerves III-XII and spinal) and their related ganglia outside the central nervous system (CNS). The latter comprising the brain and spinal cord. The central nervous system and peripheral nervous system together form the nervous s...
Diffuse astrocytoma MYB or MYBL1 altered is a newly recognized pediatric brain tumor type included in the 5th Edition (2021) WHO brain tumor classification 1.
This tumor has been identified as a distinct pediatric entity from "adult-type" IDH-wt/H3-wt diffuse gliomas based on MYB o...
Delayed posthypoxic leukoencephalopathy (DPHL) is a demyelinating syndrome presenting as an acute neurological deterioration shortly after apparent recovery from a hypoxic-ischemic episode.
Given its low frequency, there are no large numbers regarding the prevalence and incidence ...
The carotid cistern is one of the basal (subarachnoid) cisterns that surrounds the supraclinoid internal carotid artery.
Relations and/or Boundaries
The carotid cistern lies between these brain structures:
medially: the optic chiasm and nerve
laterally: the mesial temporal lob...
Desmoplastic myxoid tumor of the pineal region, SMARCB1-mutant is a rare and recently described type of pineal parenchymal tumor encountered in adults.
Desmoplastic myxoid tumor of the pineal gland SMARCB1-mutant occurs in adolescents and young adults (mean age of diagnosis 40 yea...
The central nervous system (CNS) is the part of the nervous system that includes the brain and spinal cord.
The main components of the CNS are the brain and spinal cord. In addition, the CNS includes the optic nerves (cranial nerve II), retinas, olfactory nerves (cranial nerve I)...
Diffuse glioneuronal tumor with oligodendroglial features and nuclear clusters is a novel glioneuronal tumor entity recently identified by a characteristic methylation profile 1.
The exact nature of diffuse glioneuronal tumors with oligodendroglial features and nuclear clusters has...
Myxoid glioneuronal tumor is a rare and low-grade tumor (WHO grade 1) that usually involve the septum pellucidum, corpus callosum, subcallosal area, periventricular white matter and septal nuclei 1.
The histologic features of this tumor are similar to dysembryoplastic neuroepithel...
GABAA receptor antibody (anti-GABAAR) encephalitis is an autoimmune encephalitis characterized by a severe seizure disorder and distinctive radiographic features.
Given the rarity of the condition, epidemiological data pertaining to anti-GABAAR encephalitis is not well established...
Febrile seizures are a largely idiopathic phenomenon which may occur between 6 and 60 months of age, defined by a seizure occurring concomitantly with a temperature over 38C (100.4F). This entity excludes seizures associated with infections of the central nervous system such as bacterial meningi...
Papillary craniopharyngiomas are WHO grade 1 tumors of the pituitary region typically presenting as mostly solid masses in adults. They are an entirely separate entity from the far more common adamantinomatous craniopharyngioma that are found at all ages but particularly in children 1,2.
Adamantinomatous craniopharyngiomas are WHO grade 1 tumors of the pituitary region typically presenting as cystic masses with peripheral calcifications in children. They are a distinct entity from the far less common papillary craniopharyngioma found in adults 1,4.
Until the 5th E...
Diffusion-negative acute ischemic stroke refers to a clinically diagnosed acute ischemic stroke without cerebral restricted diffusion on DWI on brain MRI.
Although DWI is highly sensitive for acute ischemic strokes, it fails in a minority of cases in its detection 1,2.
It is not ...
A commissure (TA: commissura) is a location at which two anatomical structures are united. Though the term most commonly refers to the commissures in the brain, there are a number which exist in the human body:
central nervous system
Intradiploic encephaloceles are a very rare form of encephalocele where there is herniation of brain tissue into the diploic space but not beyond. They have usually been described post-trauma but have also rarely been described in non-traumatic situations 1.
These result from brain p...
Multisystemic smooth muscle dysfunction syndrome is a rare genetic disorder caused by mutations in the ACTA2 gene, resulting in intracranial steno-occlusive disease and aortic dissection or aneurysm, among other complications.
Most cases are diagnosed in childhood 1.
Ring-shaped lateral ventricular nodules (RSLVNs) are small nodular ring-shaped lesions attached generally to the ependyma of the roof and body of the lateral ventricles.
They are incidental findings and are of no reported clinical significance 1.
These nodules are rare and their ...
The trochlea is a cartilaginous structure acting as a pulley for the superior oblique muscle of the eye.
The trochlea inserts on the trochlear fovea and spine located on the anteromedial part of the orbital roof. The tendon of superior oblique muscle passes through it 1.
Symmetrical cerebral T2/FLAIR hyperintensities are seen in a broad range of pathologies. The differential depends essentially on the location of the lesions.
Symmetrical corticospinal tract lesions
amyotrophic lateral sclerosis
symmetrical T2/FLAIR hyperintensities along the corticospinal tra...
Elsberg syndrome is an established but rarely recognized cause of cauda equina syndrome and lower thoracic myelitis, associated with a presumed infectious etiology.
Elsberg syndrome is likely responsible for 10% of combined cauda equina syndrome and myelitis 1.
Cerebellar restricted diffusion refers to a hyperintense signal involving the cerebellum on DWI images with a corresponding low signal on ADC images.
Vascular thrombo-occlusive disease
cerebellar arterial infarction 1
superior cerebellar arterial infarct
Vestibular paroxysmia describes a clinical syndrome of sudden and stereotyped episodes of vertigo-type symptoms which usually last for less than one minute, often attributed to being a nerve compression syndrome affecting the vestibular nerve.
Vestibular paroxysmia most commonly m...
Nestin is an intermediate filament protein found primarily in central nervous system stem cells. It is the target of antibodies for immunohistochemistry for the assessment of neuropathological histology specimens.
Progressive muscular atrophy is one of the motor neuron diseases, sometimes considered a variant of amyotrophic lateral sclerosis, confined to the lower motor neurons.
The dual stream language processing models (dorsal and ventral) have replaced the historic model that only included the Broca's and Wernicke's areas and the arcuate fasciculus 1.
The dorsal stream is responsible for phonological processing and language production (sound/sign to actio...
Skull base meningiomas can be located at the olfactory groove, tuberculum sella, sphenoid ridge, petroclival region, foramen magnum and jugular foramen 1.
Similar to typical meningiomas, they are slowly growing and usually asymptomatic. Apart from headache, they can pre...
Amyloid related imaging abnormalities (ARIA) represent a variety of imaging features identified in patients with Alzheimer disease being treated with novel amyloid lowering therapies such as the monoclonal antibodies bapineuzumab, solanezumab and aducanumab 1-4.
In most ...
Low back pain, lumbar or lumbosacral pain is an extremely common clinical symptom and the most common musculoskeletal condition affecting the quality of life that can be found in all age groups. It represents the leading cause of disability worldwide 1-3.
Low back pain is a very c...
Cerebral palsy is a spectrum of developmental disorders that result from an insult to the developing brain in utero or early life. Characteristically, muscle tone and movement are affected but there is wide variation in the degree to which each individual is affected 1.
A mnemonic to remember the commonest clinical signs of Parkinson disease is
S: shuffling gait
M: mask-like facies
A mnemonic to remember the nerve supply to the scalp is:
G: greater occipital nerve / greater auricular nerve
L: lesser occipital nerve
A: auriculotemporal nerve
S: supratrochlear nerve
S: supraorbital nerve
Please note that other nerves also contribute, see anatomy articl...
A mnemonic to remember the commonest causes of seizures is:
A: AV malformation
A mnemonic to remember the signs of cerebellar disease is:
I: intention tremor
S: slurred speech
A mnemonic to remember the commonest signs of Horner syndrome is:
L: loss of ciliary-spinal reflex
Rosenbach sign may refer to several different clinical signs:
Rosenbach sign (AV regurgitation)
Rosenbach sign (eye)
Rosenbach sign (hemiplegia)
History and etymology
Ottomar Ernst Felix Rosenbach (1851-1907), a German physician born in Prussian County in Silesia, graduated from medicine in...
Tobacco abuse, most commonly by smoking cigarettes, is a legal drug habit of many throughout the world. It is a significant risk factor for many malignancies, respiratory and cardiovascular diseases and is a major cause of premature mortality throughout the world.
It has been esti...
Rosenbach sign or phenomenon is a clinical sign described in hemiplegia.
The sign refers to the absence of an abdominal wall skin reflex when stroking the paralyzed side of a patient; conversely on the unaffected side, the reflex is normal 1.
Rosenbach gave his name to two other cli...
Pituitary height grading describes degrees of loss of the pituitary height (concavity), which encompasses gradations of (partially) empty sella.
As originally described by Yuh et al. 1, the loss of pituitary height (h) and the sellar height (H) are measured on a midsagittal T1-weighted...
The arterial transit artifact, sometimes known as the bright vessel appearance or trapped labeled spins, on noncontrast arterial spin labeling (ASL) MR perfusion of the brain refers to curvilinear high signal corresponding to labeled blood within cerebral arteries. Normally, in ASL imaging, labe...
The shrimp sign is an MRI marker of cerebellar progressive multifocal leukoencephalopathy, characterized by T2-hyperintensity in the cerebellar white matter abutting but sparing the dentate nucleus.
The white matter lesion resembles a shrimp, with the dentate nucleus outlining the belly of the ...
Paracetamοl (or acetaminοphen in North America) is the most widely used drug in the world. It is employed as an antipyretic and mild analgesic in both adults and children. Although once regarded as a benign agent, it is now viewed with increasing concern due to its acute hepatotoxicity following...
Response assessment in neuro-oncology brain metastases (RANO-BM) criteria are recommendations for standardized tumor response and progression assessment in clinical trials involving brain metastases. Published in 2015, these should not be confused with the RANO criteria for high-grade glioma fro...
The anococcygeal nerve is the terminal branch of the coccygeal plexus and is described as supplying the skin of the post anal region.
The anococcygeal nerve originates from the coccygeal plexus 2.
The course of the anococcygeal nerve varies according to source i...
The coccygeal plexus is formed by the anterior rami of S4-S5 in combination with the coccygeal nerve and is described as supplying the skin of the post-anal region.
The plexus consists of a minute network of nerve fibers contributed by the anterior rami of S4, S5 and the ...
Uhthoff phenomenon refers to the temporary exacerbation (lasting less than 24 hours) of neurological symptoms secondary to increases in body temperature. This phenomenon is experienced by multiple sclerosis patients, though it also occurs in other demyelinating diseases 1.
History and etymolog...
Meningiomatosis, specifically familial meningiomatosis, is a rare tumor predisposition syndrome characterized by multiple meningiomas. This entity is defined in patients that do not meet diagnostic criteria for the more common neurofibromatosis type 2, which also features a predisposition to men...
Hypertensive brainstem encephalopathy (HBE) is a clinicoradiological diagnosis characterized by severe hypertension (SBP >200mmHg), vasogenic edema of the brainstem, and a variable presentation of acute-subacute neurological disturbances. One of the primary diagnostic features often seen is the ...
The veins of the brainstem drain the medulla, the pons and the mesencephalon, including the cerebral peduncles, tegmentum and quadrigeminal plate. They are characterized by several variations and feature multiple connections draining into the inferior, medial superior petrosal sinuses or form a ...
The transverse pontine veins course in a horizontal fashion along the anterior surface of the pons at different heights above or below the trigeminal nerve.
The transverse pontine veins connect the anterior pontomesencephalic vein to the veins on the lateral pontine surface inclu...
The peduncular veins (PV) or interpeduncular veins are veins of the brainstem and tributaries of the basal vein of Rosenthal, sometimes visible on imaging in the vicinity of the basilar artery tip and the proximal posterior cerebral artery.
The peduncular veins drain the cerebral...
The anterior medullary vein (AMV) is a vein of the brain stem that can be seen in several individuals. It connects the anterior spinal vein to the pontomesencephalic venous system and several adjacent dural sinuses via bridging veins.
The anterior medullary vein usually courses i...
The lateral mesencephalic veins (LMV) form an important supratentorial-infratentorial anastomosis from the basal veins of Rosenthal to the superior petrosal sinus.
The lateral mesencephalic veins usually course through or near the lateral mesencephalic sinus. They receive venous ...
The anterior pontomesencephalic vein (APMV) is a longitudinal vein running along the anterior surface of the pons and mesencephalon and in the interpeduncular fossa. Uncommonly it can become large and can potentially lead to confusion on imaging. In a midline position, it is called the median an...