Basal ganglia and thalamus signal abnormalities occur in a wide variety of conditions. Ischaemia/hypoxia, metabolic disorders and toxins, particularly those that affect the respiratory chain, have a predilection for affecting the basal ganglia as they are highly metabolically active.
They can ...
Basal ganglia calcification is common and is seen in approximately 1% of all CT scans of the brain, depending on the demographics of the scanned population. It is seen more frequently in older patients and is considered a normal incidental and idiopathic finding in an elderly patient but should ...
There are many causes of basal ganglia T1 hyperintensity, but the majority relate to deposition of T1-intense elements within the basal ganglia such as:
calcium and phosphate abnormalities
acquired non-wilsonian hepatocerebral degeneration
The causes of basal ganglia T2 hyperintensity can be remembered using the mnemonic LINT:
venous infarction (internal cerebral vein thrombosis)
neurodegenerative / metabolic
autoimmune encephalitis (e.g. anti-D2 dopamine antibody encephalitis)
Basal ganglia T2 hypointensities can be caused by any of the following and is commonly remembered using the mnemonic ChOMP.
Parkinson disease: more in globus pallidus
Parkinson-plus syndrome: more in putamen
deoxyhaemoglobin of haemorrhage
Basilar invagination, also called basilar impression, is a congenital or acquired craniocervical junction abnormality where the tip of the odontoid process projects above the foramen magnum.
The terms basilar invagination and basilar impression are often used interchangeably becau...
Involvement of both middle cerebellar peduncles is uncommon, but has a relatively long list of differential diagnoses, including 1:
multiple systemic atrophy (MSA)
Calcification of the globe has many causes, varying from the benign to malignant. When calcification is seen of the posterior half of the globe, it could relate to any of the layers (scleral, choroidal or retinal), as it is not possible to separate them out on CT.
drusen: 1% population...
Calvarial thickening can occur from a number of causes. These include:
chronic ventricular shunting 1
anaemias (largely associated with massive haematopoiesis)
Carotid artery stenosis also known as extracranial carotid artery stenosis, is usually caused by an atherosclerotic process and is one of the major causes of stroke and transient ischaemic attack (TIA) 1.
This article refers to stenosis involving carotid bulb and the proximal segment of intern...
A cavernous sinus mass has a wide differential including:
orbital apical inflammation with cavernous sinus involvement (Tolosa-Hunt syndrome)
any of the cranial nerves traversing the cavernous sinus: III, IV, V (V1 and V2) and VI
trigeminal schwannoma is ...
Cerebellopontine angle (CPA) masses are relatively common. Although a diverse range of pathologies may be seen in this region, the most common by far is a vestibular schwannoma.
Cerebellopontine angle masses can be divided into four groups, based on imaging characteristics:
Cerebral atrophy is the morphological presentation of brain parenchymal volume loss that is frequently seen on cross sectional imaging. Rather than being a primary diagnosis, it is the common endpoint for range disease processes that affect the central nervous system. Though often no identifiabl...
Cerebral herniation, also referred to as acquired intracranial herniation, refers to shift of cerebral tissue from its normal location, into an adjacent space as a result of mass effect. It is a life-threatening condition that requires prompt diagnosis.
There are a number of differe...
The differential for peripheral or ring enhancing cerebral lesions includes:
demyelination (incomplete ring)
tumefactive demyelinating lesion (incomplete ring)
Vascular malformations of the central nervous system can be divided, as they can elsewhere, into high and low flow malformations.
arteriovenous malformation (AVM)
cerebral AVM (pial/parenchymal AVM)
cerebral proliferative angiopathy
dural arteriovenous fistula (DAVF)
Cervical spine injuries can involve the cervical vertebral column, intervertebral discs and cervical spine ligaments, and/or cervical spinal cord. The cervical spine accounts for ~50% of all spinal injuries.
5-10% of patients with blunt trauma have a cervical spine injury 1.
Chorioretinitis refers to inflammation of the retina and choroid. As a delayed sequelae, it is one of the causes of calcification of the globe. It is often considered a form of posterior uveitis.
various congenital infections such as 2,3
rubella: ocular rubella
There are several viral and prion infections which can result in a chronic encephalitis with slow progression into brain atrophy. These have a very poor prognosis with no effective treatment.
Some of these include:
progressive multifocal leukoencephalitis
subacute sclerosing panencephalitis
The differential of a mass involving or arising from the clivus is a relatively narrow one and can be divided into whether the lesion arises from the skull base itself, the intracranial compartment above or the base of skull below.
When evaluating the clivus it is important to compare the marro...
Colpocephaly is a descriptive term for a disproportionate prominence of the occipital horns of the lateral ventricles. It can result from a wide range of congenital insults.
Patients may present with motor abnormalities, cognitive deficit, visual abnormalities, and seizur...
Communicating hydrocephalus is a type of hydrocephalus where CSF is able to leave the ventricular system.
Communicating hydrocephalus is commonly used as the opposite of obstructive hydrocephalus which leads to much unnecessary confusion, as most causes of communicating hydrocepha...
Complications of cranial radiation therapy are fairly common, particularly in long-term survivors, and especially in paediatric patients.
Cranial radiotherapy is used for a variety of brain tumours, either in isolation or in combination with concurrent chemotherapy. Complications from irradiati...
Congenital calvarial defects are a group of disorders characterised by congenital calvarial bone defects that vary in severity.
CT with 3D shaded surface reformats is the best imaging tool as it demonstrates calvarial defects and bone margins:
Congenital ventriculomegaly can have a large number of syndromic associations.
fetal alcohol syndrome
Convexal subarachnoid haemorrhages (cSAH) are non-traumatic intracranial haemorrhages that occur within the surface sulci of the brain (cf. basal cisternal distribution of aneurysmal SAH).
There are various causes of convexal subarachnoid haemorrhage, some of which include:
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...
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
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 ...
Demyelinating disorders are a subgroup of white matter disorders characterised 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)
Most tumours of the CNS can potentially occur in the temporal lobe, but entities with a predilection for being diagnosed in this location include:
pleomorphic xanthoastrocytoma (PXA)
dysembryoplastic neuroepithelial tumour (DNET)
multinodular and vacuolat...
Diffuse atrophy of the cerebellum refers to a progressive and irreversible reduction in cerebellar volume. It is a relatively common finding and found in a wide variety of clinical scenarios.
Diffuse cerebellar atrophy can be difficult to distinguish from global cerebellar hypopla...
Dural arteriovenous shunts (DAVS) are rare congenital arteriovenous malformations (CAVMs). On the basis of clinical and anatomical features DAVS have three different types:
dural sinus malformations (DSMs)
infantile or juvenile DAVS (IDAVS)
adult DAVS (ADAVS)
Dural ectasia refers to ballooning or widening of the dural sac which can result in posterior vertebral scalloping and is associated with herniation of nerve root sleeves.
Patients with dural ectasia may present with low back pain or radicular pain in the buttocks or legs...
Pachymeningeal enhancement, also known as dura-arachnoid enhancement 4, refers to a dural and outer layer of arachnoid pattern of enhancement seen following contrast administration and may occur in the conditions listed below:
Dural masses can be the result of a number of different tumours and conditions, although meningiomas are by far the most common. The differential of a dural mass includes:
primary dural lymphoma
solitary fibrous tumour of the dura
Ectopia lentis refers to subluxation or dislocation of the lens of the eye secondary to dysfunction or disruption of zonular fibres.
systemic and syndromic disorders
typically upwards and out
most common spontaneous cause 2
homocystinuria - ty...
Elevated prolactin can be due to a number of causes, including elevated production/secretion as well as reduced inhibition.
Prolactin is controlled by numerous homeostatic mechanisms, with tonic secretion of prolactin inhibitory hormone (dopamine) by the hypothalamus having a dominant effect 1...
Empyemas are purulent inflammatory collections within a body cavity. Contrast this with abscesses, which arise within parenchymal tissue, rather than occupying a pre-existing anatomical space.
Colloquially, the standalone term empyema is used to refer to thoracic empyemas but there...
Although sporadic viral encephalitis is most commonly due to herpes simplex virus 1 (HSV-1) the extended herpesvirus family consists of many other viruses many of which can also infect the central nervous system. Encephalitis due to herpesvirus family include 1:
herpes simplex virus 1 (HSV-1)...
An enlarged posterior fossa 'CSF' space posterior to the cerebellum has a number of differentials that include:
mega cisterna magna
Careful attention to the cerebellum needs to paid as also to be considered are:
Enlargement of sella turcica can be seen in situations including the following:
empty sella syndrome
slight globular enlargement of the sella with no erosion, destruction or posterior displacement of dorsum sellae
enlargement with erosion of anterior cortex of dorsu...
Epilepsy is a common neurological disorder that has a varied presentation and requires two or more unprovoked seizures at least 24 hours apart for diagnosis. MRI is the modality of choice for epilepsy, most often investigating for an underlying cause, especially in adults.
Epiphora (plural: epiphoras) represents excessive tearing of the eye and is a common clinical presentation to ophthalmological practice. It is most frequently due to an obstruction of the nasolacrimal drainage apparatus. Less commonly, overproduction of tears may be responsible.
Extra-axial is a descriptive term to denote lesions that are external to the brain parenchyma, in contrast to intra-axial which describes lesions within the brain substance.
Often it is trivially easy to distinguish an intra-axial from an extra-axial mass. In many cases,...
Extra-axial masses of the intracranial compartment have a wide range of differentials, ranging from benign developmental cysts to malignant tumours.
choroid plexus papilloma/carcinoma
cranial nerve schwannoma
Extraconal orbital lesions include lesions which arise from structures within the extraconal orbital space and those extending from adjacent structures into the orbits.
dermoid cyst: most common lesion in paediatrics
lacrimial gland lesions
Extraneural spread of primary intracranial neoplasm is distinctly uncommon, occurring far less frequently than CSF spread.
The most frequent neoplasms to do so, in decreasing order of frequency, are:
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...
Fetal brain tumours are uncommon and tends to have very different pathological spectrum than that observed in adults; in order of decreasing frequency:
fetal intracranial teratoma: most common tumour by far
astrocytoma/glioblastoma: next most common
craniopharyngioma: papillary type
Fetal intracranial calcification refers to intracranial calcification detected in utero. This can arise from a number of pathologies which include:
in utero infections
fetal toxoplasmosis infection: calcification tends to be randomly distributed
fetal cytomegalovirus infection1: calcificatio...
Fetal intracranial cystic lesions can arise from a number of pathologies, including:
fetal arachnoid cyst
fetal choroid plexus cyst
fetal connatal cyst
fetal porencephalic cyst
fetal interhemispheric cyst
fetal subependymal cyst
dorsal cyst of holoprosencephaly
Fetal intracranial haemorrhage may occur either within the cerebral ventricles, subdural space or infratentorial fossa.
Haemorrhages can occur in a number of situations:
mechanical trauma, e.g. maternal abdominal blunt or birth trauma
severe fetal hypoxia
background fetal thromboc...
Fetal ventriculomegaly (ventricle width >10 mm) is an important finding in itself and it is also associated with other central nervous system abnormalities. For more information, see the main article fetal ventriculomegaly.
Fetal ventriculomegaly can be thought of in ter...
Focal calvarial thinning can result from a number of causes. They include:
bilateral thinning of the parietal bones (normal variant) most common
mega cisterna magna
peripherally located tumours (e.g. oligodendroglioma)
Gyral enhancement, also known as gyriform, cortical, or grey matter enhancement, is a pattern of contrast enhancement in the superficial brain parenchyma that conforms to the serpentine morphology of the cerebral gyri. It should be distinguished from leptomeningeal enhancement, which is also ser...
Haemorrhagic intracranial metastases are considered to represent between 3-14% of all cerebral metastases (cf. 1-3% of gliomas are haemorrhagic).
These classically originate from:
renal cell carcinoma
thyroid carcinoma: papillary carcinoma of the thyroid has the hig...
Hiccups (or hiccoughs), medical term singultus (rarely used), are an unpleasant phenomenon, experienced by everyone on occasion, and usually self-limiting. However the much rarer intractable chronic form can be extremely debilitating.
Hiccups are a symptom that has probably been e...
The CNS manifestations of HIV/AIDS (neuroAIDS) occur secondary to a wide range of neurodegenerative, infectious, inflammatory, or neoplastic processes.
Since the introduction of highly active antiretroviral therapy (HAART) in 1996, there has been a shift in the epidemiology of CN...
Holocord presentation refers to a process which involves the spinal cord, from cervicomedullary junction to the tip of the conus. It does not relate to a specific condition nor does it distinguish between involvement by cystic expansion or solid tumour, or by a combination of both. It merely den...
Distinguishing primary hydrocephalus from atrophy resulting in compensatory enlargement of the CSF spaces as the cause of ventriculomegaly can be, at times, challenging in image interpretation.
Features that favour hydrocephalus include:
dilatation of the temporal horns
Hyperattenuating cerebral metastases on CT can be due to haemorrhage, calcium, or highly cellular tumours.
There is overlap between the entities, with some cerebral metastases appearing in more than one list 1-6:
haemorrhagic cerebral metastases (mnemonic)
Hypomyelinating disorders are a heterogeneous subset of white matter disorders characterised by abnormally low amounts of myelination.
In distinction to other myelin disorders, hypomyelination is a permanent deficiency in myelin deposition rather than myelin destruction (i.e. demyelination) or ...
Hypothalamic lesions are numerous representing some entities that are unique to the hypothalamus, as well as many lesions that can be seen elsewhere within the brain. Additionally, due to its proximity to the optic chiasm, third ventricle and pituitary region, many lesions of these locations can...
Intracranial arterial beading represents alternating areas of constriction in the intracranial arteries that gives the appearance of beads strung together.
The various conditions where this may be seen are:
cerebral vasospasm post...
Intracranial cystic lesions in the perinatal period can carry a relatively wide differential which includes:
Supratentorial cystic lesions
choroid plexus cyst
The following intracranial lesions may show high signal on diffusion-weighted imaging (DWI):
lesions with intense high signal
cytotoxic cerebral oedema
intracranial epidermoid cyst
lesions with variable or moderately high signa...
Intracranial metastases from non-CNS primary neoplasms are becoming more common due to significant advances in cancer treatment over the last few decades. Increasing numbers of patients live longer and present with metastasis in locations considered unusual previously:
brain (parenchymal) metas...
A variety of intracranial tumours exhibit different forms of calcification. Some lesions commonly show calcification while in some tumours, calcification is seen only in few number of cases. In this article these tumours are classified on the basis of frequency of calcification.
Intradural extramedullary neoplasms are located outside the spinal cord but within the dural sheath.
The majority (70-80%) of spinal canal tumours are intradural extramedullary 1.
Patients present with signs and symptoms of spinal cord or nerve root compre...
Intralaminar dural haematomas in the intracranial space, are exceedingly rare, and represent haemorrhage between the two layers of the dura mater. As a result, it has distinctive features allowing it to be distinguished from extradural haematomas but mimics subdural haematomas. They are equivale...
Intraventricular metastases are a very rare finding. A few intracranial tumours and some extracranial tumours metastasise to the ventricles. The most common site of intraventricular metastasis is the trigone of the lateral ventricles due to high vascularity of the choroid plexuses. The next most...
Intraventricular neoplasms are rare and arise from periventricular structures such as the walls of the ventricular system, the septum pellucidum and the choroid plexus. Many tumour types arise from, or can bulge into the ventricular system, although there are certain lesions that are relatively ...
A J-shaped sella is a variant morphology of the sella turcica, whereby the tuberculum sellae is flattened, thus forming the straight edge of the "J". The dorsum sellae remains rounded and forms the loop of the "J".
Differential diagnosis for a J-shaped sella includes 1,2...
Lead poisoning or plumbism is a multisystem condition due to the way in which lead interferes with the function of virtually every organ system. Plumbism most severely manifests due to its devastating effects on the CNS, but it also has important deleterious consequences on the skeletal, renal, ...
Leptomeningeal enhancement refers to a diffuse or focal gyriform or serpentine enhancement that can be seen in the following conditions:
tuberculous meningitis (can also be focal)
CNS cryptococcal infection
coccidioidal meningitis (c...
Lesions of the corpus callosum are uncommon and arise from multiple different aetiologies. The lesions can be classified according to underlying pathophysiology 4-6.
agenesis of the corpus callosum
enlarged perivascular spaces
tubonodular pericallosal lipoma: associated with dysge...
Longitudinally extensive spinal cord lesions (LESCL), also known as longitudinally extensive transverse myelitis (LETM), represent extensive involvement of the spinal cord, with abnormal T2 signal traversing at least three vertebral body segments in length.
They are typi...
Lytic skull lesions have a relatively wide differential that can be narrowed, by considering if there are more than one lesion and whether the mandible is involved.
lytic skeletal metastases
epidermoid - scalloped border with a sclerotic rim
The increased globe size or macrophthalmia may have many differentials:
buphthalmos (congenital glaucoma)
macrophthalmus in neurofibromatosis type 1 (NF1)
connective tissue disorders: Marfan syndrome, Ehlers-Danlos syndrome
The differential diagnosis of masses arising from the foramen of Monro can be approached depending on the age of the patient.
choroid plexus papilloma
Langerhans cell histiocytosis
subependymal giant c...
Meckel cave lesions are numerous. The aim of this article is to list them in an easy way for revision and assessment of differential diagnosis.
Meckel cave tumours account for only 0.5% of all intracranial tumours. The most common histologies include:
trigeminal schwannoma: most c...
Medical devices in the abdomen and pelvis are important to be recognised, just like medical devices of the chest. Often we ignore these devices, considering them to be incidental and non-pathological, however it is essential to be aware of potential complications.
Medical devices in the neck are regularly observed by radiologists on plain film and CT reporting. They include devices which pass through the neck into the chest and stomach or ascend to/into the head.
Vascular access devices
peripherally inserted central catheters (PICC)
Meningeal enhancement is a generic term related to the enhancement of the membranes that envelop the brain and spinal cord. Due the anatomical features, this enhancement can be divided in two subtypes:
leptomeningeal enhancement (pial or pial-arachnoid enhancement)
pachymeningeal enhancement (...
Meningoceles are protrusions of the meninges through a defect or weak point in the skull or spine, usually involving the soft tissues beneath the surface of the skin. They are typically categorised into congenital, iatrogenic (e.g. following a craniotomy, sinus surgery, or as a laminectomy compl...
One of the most important indicators of increased intracranial pressure due to mass effect is midline shift.
Any intra-axial or extra-axial lesion (tumour, haemorrhage, abscess, etc) has the potential to exert mass effect on the brain parenchyma and cause lateral shift of the midline...
There are numerous mitochondrial disorders that affect the neurological and muscular systems in a variety of ways:
mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS)
myoclonus epilepsy with ragged red fibres (MERRF)
A mixed cystic and solid pituitary region mass has a limited differential.
both papillary (more solid) and adamantimonatous (more cystic)
cystic change / necrosis / previous haemorrhage
Most other solid and enhancing pituitary region ma...
Mostly/purely cystic pituitary region masses have a small differential.
Rathke's cleft cyst
craniopharyngioma (adamantimonatous type): 90% have calcification
Moyamoya syndrome, also termed the moyamoya pattern or phenomenon, is due to numerous conditions that can cause arterial occlusion of the circle of Willis, with resultant collaterals, and appearances reminiscent of moyamoya disease. These conditions include 1-4 :
vessel wall abnormalities
The most common causes of multiple cranial nerve thickening and enhancement include:
metastasis (most common)
neurofibromatosis type II
lymphoma and leukaemia
chronic inflammatory demyelinating polyneuropathy
cranial nerve enhancement: for compl...
Intracranial calcifications are common in certain locations and often are of no clinical concern.
The two most commonly encountered types of calcification include:
normal age-related intracranial calcifications
intracranial arterial atherosclerosis
Concerning calcifications are much less co...