Congenital muscular dystrophies (CMD) are a heterogeneous group of autosomal recessive myopathies presenting at birth with hypotonia, delayed motor development, and early onset of progressive muscle weakness, confirmed with a dystrophic pattern on muscle biopsy.
Congenital anomalies of the ossicles are most frequently associated with external ear abnormalities also, although they can occur in isolation.
They cause conductive hearing loss (CHL).
When bilateral they are most frequently genetic, with autosomal dominant inheritance, whereas unilateral a...
Congenital spinal meningoceles are developmental anomalies of meningothelial elements displaced into the skin and subcutaneous tissues.
Please refer on menigocele article for a broad overview of all types of this condition.
It is defect of the neural tube, an embryonic structure th...
Congenital ventriculomegaly can have a large number of syndromic associations.
fetal alcohol syndrome
A conjoined root is a type of developmental anomaly involving a nerve root. It is the most common nerve root developmental anomaly of the cauda equina being twice as common as two roots in the same foramen, the next most common anomaly.
The incidence in cadaveric studies is about ...
Connatal cysts, also known as coarctation of the lateral ventricles or frontal horn cysts, are cystic areas adjacent to the superolateral margins of the body and frontal horns of the lateral ventricles and are believed to represent a normal variant.
The incidence is 0.7% in low bi...
Contrast-induced neurotoxicity, also known as iodinated contrast-induced encephalopathy, is a rare complication of iodinated intravascular contrast resulting in a usually temporary neurological deficit. CT imaging findings can be dramatic, demonstrating contrast staining and oedema, but spontane...
The conus medullaris is the terminal end of the spinal cord.
After the cord terminates, the nerve roots descend within the spinal canal as individual rootlets, collectively termed the cauda equina. The conus medullaris most commonly terminates at the L1/2 intervertebral disc leve...
Conus medullaris syndrome is caused by an injury or insult to the conus medullaris and lumbar nerve roots. It is a clinical subset of spinal cord injury syndromes. Injuries at the level of T12 to L2 vertebrae are most likely to result in conus medullaris syndrome.
The conus medullari...
Convexal subarachnoid haemorrhages (cSAH) are nontraumatic intracranial haemorrhages that occur within the surface sulci of the brain (c.f. basal cisternal distribution of aneurysmal SAH). There are various causes of convexal SAH, some of which include:
dural venous sinus thromboses
Convolutional markings are normal impressions of the gyri on the inner table of the skull, seen predominantly posteriorly. If they are pronounced and over the more anterior parts of the skull, then this is referred to as a copper beaten skull and raises the possibility of raised intracranial pre...
Copper beaten skull, also known as beaten brass skull, refers to the prominence of convolutional markings (gyral impressions on the inner table of the skull) seen throughout the skull vault.
The appearance of copper beaten skull is associated with raised intracranial pres...
Copper deficiency myeloneuropathy is rare but increasingly recognised as a cause of neurological impairment, presenting similarly to subacute combined degeneration of the cord secondary to B12 deficiency.
Patients typically present with a proprioceptive loss, due to dors...
The cord sign refers to cordlike hyperattenuation within a dural venous sinus on non-contrast enhanced CT of the brain due to dural venous sinus thrombosis. The sign is most commonly seen in the transverse sinus because along the origin of the tentorium it runs approximately in the axial plane s...
The corona radiata refer to a pair of white matter tracts seen at the level of the lateral ventricles. Superiorly they are continuous with the centrum semiovale. Inferiorly these tracts converge as the internal capsule.
The corpora quadrigemina (Latin for "quadruplet bodies") are the four colliculi, two inferior and two superior, that sit on the quadrigeminal plate on the posterior surface of the midbrain.
The corpora quadrigemina are reflex centres involving vision and hearing:
superior colliculi: involved i...
The corpus callosum is the largest of the commissural fibres, linking the cerebral cortex of the left and right cerebral hemisphere. It is the largest fibre pathway in the brain.
located inferior to the cerebral cortices, and superior to the thalamus
connects left and right cerebral h...
A useful mnemonic to remember the causes of corpus callosum hyperintensity is:
I MADE A PHD
I: infections (e.g. tuberculosis, varicella, rotavirus, HSV)
M: Marchiafava-Bignami syndrome
A: AIDS encephalopathy
D: diffuse axonal injury and diffuse vascular injury
Corpus callosum impingement syndrome (CCIS) is caused by impingement of the corpus callosal fibers against inferior free margin of the falx cerebri due to longstanding and severe hydrocephalus and stretching of the lateral ventricles. this results in ischaemia and eventually atrophy of the neura...
A useful mnemonic to help remember the parts of the corpus callosum, from anterior to posterior, is:
Remember Genu Before Splenium
Remember G Before S (as G comes before S alphabetically)
B: body (trunk)
The corpus striatum is a collective name given to the caudate nucleus and lentiform nucleus.
History and etymology
The term originates from the Latin "striatus", meaning "striped", referring to the caudatolenticar bridges of grey matter crossing the internal capsule from the putamen to the cau...
Cortical blindness is a condition resulting from lesions in the primary visual cortex (V1) characterised by visual impairment but with an intact anterior visual pathway (normal pupillary reflexes and fundal appearance).
The degree of visual impairment is related to the extent...
Cortical laminar necrosis, also known as pseudolaminar necrosis, is necrosis of neurons in the cortex of the brain in situations when supply of oxygen and glucose is inadequate to meet regional demands. This is often encountered in cardiac arrest, global hypoxia and hypoglycaemia.
A handy mnemonic to recall cortically-based brain tumours is:
P: pleomorphic xanthoastrocytoma
D: dysembryoplastic neuroepithelial tumour (DNET); desmoplastic infantile astrocytoma and ganglioglioma
Cortical tubers or subcortical tubers (with involvement of the underlying white matter) are a common finding in tuberous sclerosis, present in 95-100% of cases 1.
These benign hamartomatous lesions can be epileptogenic foci, and are important to diagnose on imaging (typically MRI) as they can a...
The cortical vein sign refers to the presence of superficial cortical veins seen on MRI and CT (particularly with contrast injection) traversing an enlarged subarachnoid space, differentiating it from the similar radiological appearance of a subdural hygroma.
Although initially proposed as a me...
Cortical vein thrombosis, also known as superficial cerebral vein thrombosis, is a subset of cerebral venous thrombosis involving the superficial cerebral veins besides the dural sinus, often coexisting with deep cerebral vein thrombosis or dural venous sinus thrombosis. It has different clinica...
Corticobasal degeneration (CBD) is an uncommon neurodegenerative disease and is one of the subset of taupathies.
The vast majority of cases are sporadic, although a number of familial cases have been described 2. Patients are usually in the fifth to seventh decades of life5, with ...
The corticorubral tract contains neurons that connect the primary motor and sensory areas to the red nucleus. The rubrospinal tract then descends through the spinal cord.
The tract is thought to excite flexor muscles and inhibit extensor muscles.
The corticospinal tract is a descending neural pathway primarily concerned with motor function extending from the motor cortex down to synapse with motor neurones of the spinal cord.
Corticospinal fibres arise from neurones in the cerebral cortex. Most of th...
The cotton wool appearance is a plain film sign of Paget disease and results from thickened, disorganized trabeculae which lead to areas of sclerosis in a previously lucent area of bone, typically the skull. These sclerotic patches are poorly defined and fluffy.
Other Paget disease re...
A coup-contrecoup injury is a term applied to head injuries and most often cerebral contusions and traumatic subarachnoid haemorrhage. It refers to the common pattern of injury whereby damage is located both at the site of impact (often less marked) and on the opposite side of the head to the po...
Coup de poignard of Michon refers to spinal subarachnoid haemorrhage, usually as a result of a spinal AVM.
Presentation is with sudden excruciating back pain, akin to being stabbed with a dagger (poignard = french for dagger). It is the corollary of the thunderclap headache.
Cowdry bodies are neuronal intranuclear inclusions seen in Herpes simplex virus infections 1.
Cowdry bodies are in fact fixation artifacts and not directly the result of the intracellular virus 2.
The cranial foramina are the holes that exist in the base of skull to allow the passage of structures into and out of the cranium:
anterior ethmoidal foramen
Enhancement of cranial nerves has a lenghy differential including 1-2:
mycobacterial: tuberculosis, leprosy
spirochetes: Lyme disease, syphilis
viruses: e.g. herpes zoster virus, influenza virus, human herpesvirus 1 (HHV1) 3
The cranial nerves are the 12 paired sets of nerves that arise from the cerebrum or brainstem and leave the central nervous system through cranial foraminae rather than through the spine.
The first and second cranial nerves derive from the telencephalon and diencephalon respectively ...
There are many cranial nerve mnemonics that can be memorable and rude/lewd. Either way, they can be helpful for remembering the names of the twelve cranial nerves, as well as remembering which nerves are sensory, motor, or both.
Remembering cranial nerve names in order of CN I to CN XII:
Craniopharyngiomas are relatively benign (WHO grade I) neoplasms that typically arise in the sellar/suprasellar region. They account for ~1-5% of primary brain tumours, and can occur anywhere along the infundibulum (from the floor of the third ventricle, to the pituitary gland).
There are two p...
Cranioplasty is the surgical intervention to repair cranial defects, and is mostly performed after traumatic injuries. The procedure is performed using different materials and techniques, with no consensus about the best option. Methyl-methacrylate is the prosthetic material most extensively use...
Craniorachischisis is a rare birth defect and the most severe of the neural tube defects. It refers to the presence of both anencephaly and spina bifida.
In one study the prevalence of craniorachischisis was 0.51 per 10,000 live births in a Texas-Mexico border population 1.
Craniosynostosis refers to premature closure of the cranial sutures. The skull shape then undergoes characteristic changes depending on which suture(s) close early.
There is a 3:1 male predominance.
Primary forms are either sporadic or familial. Secondary craniosynosto...
Craniotomy is a surgical procedure where a piece of calvarial bone is removed to allow intracranial exposure. The bone flap is replaced at the end of the procedure, usually secured with microplates and screws. If the bone flap is not replaced it is either a craniectomy or cranioplasty.
Creatine is one of the compounds examined in MR spectroscopy. It resonates at 3.0 ppm chemical shift and is found in metabolically active tissues (brain, muscle, heart) where it is important in storage and transfer of energy. It tends to be maintained at a relatively constant level, and is predo...
Creutzfeldt-Jakob disease (CJD) is a spongiform encephalopathy that results in a rapidly progressive dementia and other non-specific neurological features and death usually within a year or less from onset.
On imaging, it classically manifests as T2/FLAIR hyperintensities within the basal gan...
The crista galli is a thick, midline, smooth triangular process arising from the superior surface of the ethmoid bone, projecting into the anterior cranial fossa. It separates the olfactory bulbs, which lie either side of it in the olfactory fossae of the cribriform plate. It serves as an anteri...
Crossed cerebellar diaschisis refers to a depression in function, metabolism, and perfusion affecting a cerebellar hemisphere occurring as a result of a contralateral focal supratentorial lesion, classically an infarct.
Other than neurological deficits and other clinica...
Cryptococcosis is a fungal infection caused by Cryptococcus neoformans, a globally distributed fungus that is commonly found in soil, especially that containing pigeon and avian droppings. Infection is acquired by inhaling spores of fungus.
Occurs worldwide without any defined en...
The CSF cleft sign in neuroimaging can be used to distinguish an extra-axial lesion from an intra-axial lesion, and is typically used in the description of a meningioma.
Classically, the cleft was regarded as representing a thin rim of CSF between tumour and brain parenchyma. However, it often ...
CSF flow studies are performed using a variety of MRI techniques and are able to qualitatively assess and quantify pulsatile CSF flow. The most common technique used is time-resolved 2D phase contrast MRI with velocity encoding.
Note, when referring to CSF flow in the context of imaging we are...
CSF rhinorrhoea refers to a symptom of cerebrospinal fluid (CSF) leakage extracranially into the paranasal sinuses, thence into the nasal cavity, and exiting via the anterior nares. It can occur whenever there is an osseous or dural defect of the skull base (cf. CSF otorrhoea).
CSF-venous fistulas are rare and only recently recognised causes of spontaneous intracranial hypotension. They are a direct communication between the spinal subarachnoid space and epidural veins allowing for the loss of CSF directly into the circulation and can be either iatrogenic or spontaneou...
The CT angiographic (CTA) spot sign is defined as unifocal or multifocal contrast enhancement within an acute primary intracerebral haemorrhage (ICH) visible on CTA source images and discontinuous from adjacent normal or abnormal blood vessels 1. It should not be present on pre-contrast images. ...
CT angiography of the cerebral arteries is a noninvasive technique allows visualization of the internal and external carotid arteries and vertebral arteries and can include just the intracranial compartment or also extend down to the arch of the aorta.
By using multidetector CT (MDCT) after int...
CT cerebral venography is a rapid technique which provides an accurate detailed depiction of the cerebral venous system.
Rapid diagnosis of cerebral venous thrombosis.
general CT contraindications such as pregnancy, claustrophobia, etc.
iodinated contrast contr...
Computed tomography (CT) cisternography is an imaging technique used to diagnose CSF rhinorrhoea or CSF otorrhoea (CSF leaks), as CT allows the assessment of the bones of the base of skull.
pre-contrast CT is performed with thin slices
3-10 mL of an iodinated non-ionic low-osmolar ...
The CT comma sign is a characteristic sign seen in head trauma. It is the presence of concurrent epidural and subdural haematomas, which gives the characteristic appearance of this sign as a "comma" shape.
CT head (sometimes termed CT brain), refers to a computed tomography examination of the of the brain and surrounding structures. It can be performed as a single non-contrast study or the combination of a non-contrast and post-contrast (delayed) study. This allows the identification of abnormal c...
The approach taken to interpreting a CT scan of the head is no doubt different depending on the circumstances and the reading clinician, however, most radiologists will go through the same steps. What follows is merely a suggested approach to interpreting a CT of the head.
An important aspect ...
A CT head standard report may not be applicable in all situations, but gives an idea of some of the areas to cover when reporting a CT head.
Standardised reports are controversial and should be used with caution.
Headache with photophobia.
CT head without ...
The subdural (blood) window can be used when reviewing a CT brain as it makes intracranial haemorrhage more conspicuous, and may help in the detection of thin acute subdural haematomas that are against the calvarium. It is a wider setting than the standard non-contrast window, and there are a nu...
CT head technique describes how a CT head is performed.
The technique for performing a CT of the head depends on the scanner available and fall into two broad camps:
volumetric acquisition (most common)
Step-and-shoot scanning was the first describe...
CT perfusion in ischaemic stroke has become established in most centres with stroke services as an important adjunct, along with CT angiography (CTA), to conventional unenhanced CT brain imaging.
It enables differentiation of salvageable ischaemic brain tissue (the penumbra) from irrevocably d...
The cuneus is a wedge-shaped region on the medial surface of the occipital lobe.
Anterosuperiorly the parieto-occipital sulcus separates the cuneus from the precuneus of the parietal lobe.
Posteroinferiorly the cuneus abuts the calcarine sulcus which separates it from...
The Cushing response/reflux occurs in the setting of raised intracranial pressure and is the triad of:
Cyanide poisoning is a cause of an acute anoxic-ischaemic encephalopathy that also has eventual chronic sequelae.
Acute cyanide poisoning is rare and often occurs after suicidal oral ingestion of cyanide-containing compounds, however there are other sources such as after smoke in...
Cyclopia refers to a rare fetal malformation characterised by a single palpebral fissure and a single midline orbit. This orbit may contain either a single globe or two separate globe.
The condition is thought to affect approximately 1 in 40,000 to 95,000 births (inclusive of stil...
Cystic glioblastoma is a descriptive term for one form of glioblastoma that contains a large cystic component, rather than being a pathological subtype.
Please refer to the main article on glioblastoma for a broad discussion on this tumour.
The main challenge in discri...
The term cystic meningioma is applied to both meningiomas with intratumoral degenerative cyst formation as well as those with peritumoral arachnoid cysts or reactive intraparenchymal cysts.
They should not be confused with microcystic meningiomas, a distinct variant, in which the cysts are mic...
A cystic spinal lesion can result from a number of disease entities. They include:
Dandy walker malformation
certain skeletal dysplasias 2
tricho-rhino-phalangeal syndrome type I
due to a tumour
Cyst of the medullary conus is a rare benign ependymal cyst of the conus medullaris which probably relates to abnormal persistence and cystic dilatation of the ventriculus terminalis or "5th ventricle". This entity can be symptomatic and present in adulthood with bladder or bowel sphincter distu...
The cyst with dot sign is seen in neurocysticercosis and represents the parasitic cyst with, usually eccentric, scolex.
It can be seen on both MRI and CT at:
the vesicular stage (CSF density / intensity cyst - denser / hyperintense scolex) and
colloidal vesicular stage (enhancement of wall an...
Cytomegalovirus (CMV) encephalitis is a CNS infection that almost always develops in the context of profound immunosuppression.
This article focus on adult infection, CMV is also one of the most frequent prenatal infections. Please, refer on congenital CMV infection for further discussion on t...
Cytotoxic cerebral oedema refers to a type of cerebral oedema, most commonly seen in cerebral ischaemia, in which extracellular water passes into cells, resulting in their swelling.
The term is frequently used in clinical practice to denote the combination of both true cytotoxic (cellular) oed...
Cytotoxic lesions of the corpus callosum (CLOCCs) represent a collection of disparate conditions that can cause signal change in the corpus callosum, usually involving the splenium.
The term cytotoxic lesions of the corpus callosum (CLOCCs) has been proposed recently 12 as a more ...
Dandy-Walker continuum, also referred as Dandy-Walker spectrum or Dandy-Walker complex, corresponds to a group of disorders believed to represent a continuum spectrum of posterior fossa malformations, characterised by inferior vermian hypoplasia and incomplete formation of the fourth ventricle w...
Dandy-Walker variant (DWv) is a less severe posterior fossa anomaly than the classic Dandy-Walker malformation (DWM) and is considered being on the lesser end of the disease spectrum in the Dandy-Walker continuum.
This term was created to include those malformations that do not mee...
Dawson fingers are a radiographic feature depicting demyelinating plaques through the corpus callosum, arranged at right angles along medullary veins (callososeptal location). They are a relatively specific sign for multiple sclerosis, which presents as T2 hyperintensities.
History and etymolog...
Deep brain stimulation is used in a variety of clinical settings, predominantly in patients with poorly controlled movement disorders. Although effective, its exact mode of function continues to be poorly understood 2.
Careful patient selection and target selection are essential if the proced...
The deep cerebral veins drain the deep white matter and grey matter that surround the basal cisterns and ventricular system. The deep veins are responsible for the outflow of approximately the inner 80% of the hemisphere. They provide useful landmarks for skull base and intraventricular surgery ...
Deep cerebral vein thrombosis is a subset of cerebral venous thrombosis involving the internal cerebral veins, often coexisting with cortical vein thrombosis or dural venous sinus thrombosis, and with different clinical presentations relying on which segment is involved.
As such please refer to...
Déjerine-Roussy syndrome, or thalamic pain syndrome, is type of central post-stroke pain syndrome caused by a stroke to the thalamus.
This syndrome should not be confused with Déjerine syndrome or Déjerine-Sottas syndrome.
Approximately 25% of all patients with sensory strokes d...
Déjerine-Sottas disease, also known as hereditary motor and sensory neuropathy type III or hypertrophic interstitial polyneuritis, is a rare hereditary motor and sensory neuropathy (HMSN).
This syndrome should not be confused with Déjerine syndrome or Déjerine-Roussy syndrome.
Delayed cerebral ischaemia (DCI) is a frequent complication of subarachnoid haemorrhage. It contributes substantially to the morbidity and mortality following subarachnoid haemorrhage. It is defined as symptomatic vasospasm related to subarachnoid haemorrhage or cerebral infarction demonstrated ...
The delta resistive index (delta RI or Δ RI) is a measurement that can be made when performing Doppler ultrasound.
In preterm babies who have hydrocephalus secondary to intraventricular haemorrhage, the delta RI can be used to determine whether decompression of the ventricular system with a...
Dementia with Lewy bodies (DLB), also known as Lewy body disease, is a neurodegenerative disease (a synucleinopathy to be specific) related to Parkinson disease (PD). It is reported as the second most common form of dementia following Alzheimer disease (AD), accounting for 15-20% of cases at aut...
Demyelinating disorders are a subgroup of white matter disorders characterized by the destruction or damage of normally myelinated structures. These disorders may be inflammatory, infective, ischaemic or toxic in origin and include 1-7:
multiple sclerosis (MS)
Demyelination is incorrectly often equated to multiple sclerosis, whereas in reality it is a generic pathological term simply describing, as the word suggests, the loss of normal myelin around axons in the central nervous system. This should be distinguished from dysmyelination where the formati...
MRI protocol for demyelinating diseases is a group of MRI sequences put together to best approach these white matter disorders characterized by the destruction or damage of normally myelinated structures. These disorders may be inflammatory, infective, ischaemic or toxic in origin.
Denervation changes in muscles can be observed in a number of settings.
in the very early stage, muscle signal may be normal
earliest change is increased T2 signal (best seen on a fat saturated T2WI such as STIR)
chronic changes are marked by muscle atrophy and fat...
The dentate gyrus is located in the mesial temporal lobe and forms part of the hippocampal formation, along with the hippocampus proper and subiculum.
The dentate gyrus receives fibres from the entorhinal cortex via the perforant path and projects fibres to the CA3 portion of the hippocampus. ...
The dentate nucleus is the largest and most lateral of the cerebellar nuclei, located medially within each cerebellar hemisphere, just posterolateral to the fourth ventricle 1.
It is part of the triangle of Guillain and Mollaret, connected to the contralateral red nucleus via the superior cere...
The denticulate ligaments are bilateral triangular lateral extensions of pia mater that anchor the spinal cord to the dura mater.
They are formed by pia mater of the spinal cord coursing in-between the dorsal and ventral nerve roots bilaterally. They function to provide stability to the spinal ...