How to Read CT Scan of Brain: Master the skill of interpretation of CT scan of Brain in 1 hour

Computerised Tomography (CT) Scanning/CT Scan/Computerised Axial Tomography (CAT Scan) of Head or Brain

Various imaging modalities used for investigating neurological disorders are:
X-Rays ( Plain radiography)
Ultrasonography
CT scan of the brain & Spine, CT scan with contrast, CT Angiography
MRI Brain and Spine, MR Angiography, MRI with contrast, MR Spectroscopy, MR Tractography, Functional MRI of the brain, MR cisternography
Angiography, Digital substraction angiography (DSA)
Myelography, CT myelogram
Positron Emission Tomography (PET) CT Scan
PET MRI
TCD ( Transcranial Doppler)
Single Photon Emission Computed Tomography (SPECT)

Plain Radiography or X-Ray skull is useful for the diagnosis of skull bone osteomyelitis, Craniovertebral junction abnormalities, Tumors of the cranial bones like osteomas, osteosarcoma,  metastasis to skull may be seen on skull X - ray films. Skull fractures in head injury & Growing skull fractures in children are diagnosed on skull radiography.

CT scan: CT scan is commonly used abbreviation of Computed Axial Tomography ( CAT ) scanning. This investigation machine was developed in 1970s and it was a most important development in the field of Neuroradiology after the development of X rays ( 1890s) and angiography (1920s and 1930s). It is a non invasive procedure and uses X-rays for the imaging. It utilizes X-Ray beam which passes through the tissue and produces a picture like x ray but in varying shades of grey.  The density of tissue changes the picture. CT scan produces axial or cross sectional ( slices) images of the body.
Computer  measures the density of the tissue through which x ray beam passes. CT scan machine uses multiple pencil beams of x ray which rotate in the gantry and pass through the body and on opposite side dosimeter measures the amount of radiation reaching it. Each cubic part of tissue is known as voxel ( in New machines about 512 voxels) . Each voxel produces a pixel. Computer measures the attenuation of the beam and assigns a Hounsfield Unit  ( HU ).
Sir Godfrey Hounsfield from England and Allan McLeod Cormack from USA shared Nobel prize in 1979 for invention of CT scan . All shades of Gray for image May be assigned a number ' HU'. Any HU value below minus 15 will appear pure black on CT film and any HU value above 155 HU will appear pure white.  Common  HU values are water zero ( 0 )
CSF in brain 10 to 16, Air minus 1000, Fat minus 60 to minus 120. Fat containing medullary bone will appear less white as compared to compact cortical bone ( HU +1000).


CT scan of the brain is the investigation of choice
For brain trauma patients, because
- it is less time consuming as compared to MRI,
-the presence of the metal ( bullet or pellets in gun shot injury, metal in stab injury) is not a contraindication,
- a trauma patient where the history of pace maker of heart or metallic implant is not known , CT scan can be done safely ( not possible to do MRI)
-CT scan utilizes X-ray so it detects bony injuries, like a fracture, depressed fracture & hematoma associated with fracture

-better delineation of acute hematoma or bleed like Extradural hematoma (EDH) as it appears hyperdense and more white as compared to brain .
CT scan brain is also an investigation of choice
For detecting subarachnoid hemorrhage ( spontaneous subarachnoid hemorrhage) due to rupture of an intracranial aneurysm

CT angiography ( CTA ) is an investigation to detect the aneurysm of the brain. It has become an important tool for detecting the site of aneurysm bleed, location , and other characteristics of the aneurysm of the brain . It is more sensitive than MR Angiography and its sensitivity is comparable to the Digital Substarction Angiography.

CT scan of the spine: Although MRI of the spine is undoubtedly the investigation of choice for spine, CT scan of the spine is still an important investigation. CT scan of the spine is required when MRI of the spine is not possible, for example, if a patient is with metal prosthesis ( spinal instrumentation with ferromagnetic material like steel), or a metallic bullet is impinged in the spinal cord following a gun shot injury. CT spine also helps in conditions like canal stenosis, bony fractures, ossified posterior longitudinal ligaments, etc.

High resolution CT scan, 3D reconstruction, CT myelogram , Perfusion Coputed Tomography , Intraoperative CT scan are other applications of CT scan.

MRI is the most important development in the field of neuroradiology after the development of X- rays, Angiography, and CT scan.
MRI is a non invasive radiological investigation. It does not expose the patient to the risk of radiation. It uses magnetic field . It provides multiplanar images, i.e, images in sagittal, coronal and axial planes.
Functional MRI is another non invasive investigation which helps in imaging of the eloquent area of the brain.
MR Spectroscopy provides the clue about the nature of the lesion and helps in identifying infective and neoplastic lesions of the brain.
Intraoperative MRI is an advanced technique for intraoperative imaging of the lesions inside the operation theater.
How to interpret MRI brain images?
MRI images are usually black & white. There are T1 weighted, T2 weighted, FLAIR , Diffusion weighted images and if contrast is given then T1 contrast images.
To identify T1 weighted image, see the ventricles. lateral Ventricles are in the center and contain CSF. 
On CT usually only Axial images are seen but on MRI Axial, Coronal and sagittal images are seen.
On T1 weighted image, CSF will appear Black (Hypointense).
On T2 weighted image , CSF will appear White ( Hyperintense).
On FLAIR ( Flow Attenuation Inversion Recovery) the intraventricular CSF will appear Black but brain edema will appear White.
Contrast images are usually T1 contrast Images. So, CSF will appear Black and some lesions like Meningioma will become white ( Hyperintense) after contrast enhancement.


PET and SPECT are nuclear neuroimaging and help in physiological assessment. PET ( Positron Emission Tomography) is further advanced to utilize CT or MRI imaging techniques and known as PET- CT or PET-MR. PET is used for detecting metastasis and recurrence of the tumor. PET scan commonly  utilizes Flurodeoxy glucose ( FDG) which is a radioactive tracer.

Digital substraction angiography ( DSA) is invasive investigation  which involves introducing a catheter and injecting intravenous contrast into the femoral artery. It is the gold standard investigation for defining an intracranial aneurysm, Arteriovenous malformation ( AVM) , vasospasm after Subarachnoid hemorrhage ( SAH) and other diseases of intracranial vasculature.

TCD ( Transcranial Doppler ): Noninvasive investigation to detect the vasospasm in a case of SAH.  Although Ultrasound is not a good investigation to detect intracranial pathologies as ultrasound waves do not cross bones, there are certain places where bone is very thin like temporal squama or areas in cranium which have windows like orbit. So, the flow of blood through the intracranial arteries may be detected through these windows. In vasospasm the vessels are narrowed and flow velocity increases. This is the basis of TCD, which is a noninvasive procedure and can be performed on bedside.

Ultrasonography can be used to detect hydrocephalus and meningomyelocele in prenatal period . USG can also detect hydrocephalus in infant as anterior fontanel is not closed.

Intraoperative USG is used for real time imaging , localization, extent of resection of the tumor after craniotomy at the time of neurosurgery.

Neuronavigation is used to localize the lesion, route of the surgery, safer trajectory, etc.

Neurointervention is a very promising development in the field of Neuro-radiology. It is not only useful for the diagnosis but it also offers to treat many ailments of the brain and spine. The ost important and exciting applications of neurointerventions are: Coiling of the intracranial aneurysms, Preoperative embolization of the vascular tumors like meningioma, Embolization of the intracranial and spinal AVMs, Stenting of the vessel.

The development of this non-invasive neuro-radiological investigation made a major impact on the investigative approach of intracranial lesions and treatment of neurological conditions. It revolutionized the treatment of neurosurgical patients. Before invention of CT, there was only X-ray, ventriculogram, angiography to detect the intracranial pathology.  X-ray was invented in year by Roentgen 1895 and cerebral angiography in 1927 by Egas Moniz. On the cerebral angiography Arteriovenous malformation (AVM) or intracranial aneurysms could be demonstrated, some pathologies were diagnosed only through indirect evidence like midline shift, pressure over the arteries, etc.

In 1979, Nobel Prize in physiology or medicine was awarded jointly to South African American physicist Allan Macleod Cormack & British electrical engineer Godfrey Hounsfield for development of computer assisted tomography.

Hounsfield scale or Hounsfield unit (HU) or Gray scale: A quantitative scale for describing radiodensity.

CT scan utilizes X-ray as its imaging source. CT machine consists of a gantry containing x-ray source and detectors. Central to the gantry is the aperture within which the patient lies.

CT scan machine is inside the CT room. The console of the CT is a computer on which monitor all cross section images are seen and analysed. The computer is separated from the CT room by a glass window. This protects the radiologist and radiographer from the repeated exposure to the X-ray radiation. 

The CT machine consists of a gantry which has a circular opening. The stretcher like part of the CT machine moves and depending on requirement of the CT imaging, the body part of the patient comes in the center of this circular opening of the gantry. For CT scan of the brain, patient lies on the stretcher part of the CT with head at center of the circular gantry. 

This gantry is hollow and open on both sides so there is no issue of claustrophobia. CT scan involves very less time as compared to MRI (Magnetic resonance Imaging) and no sound is produced in this process, so CT is less time consuming and more comfortable for the patient as compared to the MRI. Moreover, patient's family member can be allowed inside the CT room and to hold the hand of the patient and making the imaging process comfortable. 

Picture showing Gantry and moving table or stretcher part of the CT machine.

The attenuation (any reduction in the strength of signal while passing through) of the X-ray beam by brain parts is measured. A pencil beam of X-ray passes through the patient’s head and a diametrically opposed detector measures the extent of its absorption. 

 

Computerized tomography (CT) has vastly improved the diagnostic accuracy of diseases of the brain. NCCT scan of brain is the investigation of choice in patients with head injury. Short duration, foreign body like metal (pellets, bullet) is not a contraindication, fracture, hematoma is clearly visible.

 

Localizer view 

The first image on CT scan is the localizer view or Scout view. 

A digital radiograph (localizer view) is obtained by maintaining the X-ray tube in a stationary horizontal position.This image indicates the body part of the patient which is being studied, The cross section levels are also marked on this image and it gives an idea about the level of the cross section and approximate number of images and distance between consecutive cross sections. In brain CT scan, usually cross sections are taken at a gap of about 1 centemeter . But sometimes 2 to 3 mm thin sections are obtained which is called high resolution CT scan (HRCT).  HRCT is usually taken for small lesions like pituitary tumors.

In brain CT the localizer view appears like lateral view of X-ray with multiple horizontal lines . The horizontal line which traverses from external acoustic meatus to outer canthus of eye ( midpoint of the lateral wall of the orbit) is usually considered as the reference line and the images below it are labelled as negative and cross sections above it are labelled as positive. 

Computer processes the relative absorption values for multiple blocks of tissue (voxels). Reconstruction of these areas on a display (pixel) provides the CT scan appearance. For routine scanning, slices are 5-10 mm wide. Slices of 1-2 mm are sometimes required for high resolution CT of orbit, or pituitary region.

Selecting different window levels displays tissues of different density more clearly. Bone window and brain window. 

CT image of brain in brain window in which the brain structures are clearly visible like ventricles and lesion in the parietal region

CT image of the patient in bone window in which the cranial bone is seen and brain structures are not seen. This window is used to see the bony changes and in this patient there is erosion of the bone and a gap (fracture) in the parietal bone

An intravenous iodinated water soluble contrast medium is administered in specific clinical conditions, e.g., abscess, brain tumor, etc. 

X-ray attenuation coefficients can be calculated  for each tissue’s small volume (voxel) and is assigned a CT number scale called the Hounsfield scale.

Metal  +4000

Bone   +1000

Acute blood ( hematoma) +100

Brain     30-40

CSF       +15

Water   zero or 0H

Fat        -100

Air        -1000

 

Structures which appear more white as compared to brain are labelled as hyperdense. So, the Hounsfield unit of normal brain tissue is 30 to 40 Hounsfield unit so any lesion of more than 40 HU will be called hyperdense lesion and it will be relatively more white as compared with appearance of the brain on CT. 

Intracranial lesions which show similar appearance of radiodensity on CT as compared to brain are labelled as isodense lesions.

The intracranial lesions which appear less white than brain on CT scan are labelled as hypodense. So the hypodense structures will be having less than 30 Hounsfield units. Brain edema appears hypodense on brain CT. Pneumocephalus contains air and appears more black as compared to brain and is hypodense. Similarly arachnoid cyst which contains CSF inside is a hypodense lesion on brain CT scan.

This diagram shows a lateral view of the face or brain or skull and the level A and B of cross sections. If CT image is taken at the level of  "A" only two cerebral hemispheres will be seen . One can start reading the CT scan from this level. This is usually the last image of CT scan of the brain. At this level , it is very easy to identify the outermost hyperdense cranial bone which appears more white as compared to the brain . Inside the cranium is cerebral hemisphere and there are two cerebral hemispheres,i.e, right and left. These two cerebral hemispheres are separated by falx cerebri in midline. Sometimes, there is physiological calcification of the falx. The cranial suture in the midline is called sagittal suture and the venous sinus inside the two layers of dura beneath the sagittal suture is sagittal sinus.

CT scan of skull at vertex,i.e., at the highest level of the skull. The hounsfield unit of brain is about 40 and hounsfield unit of skull bone is about 1000 HU. Cranial bone is more hyperdense as compared to the brain tissue. Falx is visible in the midline separating the two cerebral hemispheres.

 

The cross section at the level of sylvian fissure shows basal ganglia. Basal ganglia are the deep seated gray matter nuclei deep inside the brain. The basal ganglia are Caudate nucleus, Lentiform nucleus (Globus Pallidus and Putamen) and Substantia nigra. This picture is important because it depicts the third ventricle in the midline as a slit like structure compressed between two thalami. The frontal horn of the lateral ventricle is seen and head of the caudate nucleus forms the floor of the frontal horn of the lateral ventricle. The globus pallidus and putamen are situated above the thalamus. Anterior limb of the internal capsule is between caudate nucleus and Globus pallidus and posterior limb of internal capsule is between thalamus and globus pallidus.

Lateral to the putamen is external capsule. It is situated between Claustrum and Putamen. Lateral to the claustrum is Insula which is embedded within Sylvian fissure.

This CT image is the cross section at the level of Sylvian fissure, third ventricle, thalamus, basal ganglia. Posterior to the third ventricle calcification of the Pineal gland is seen.

A large surface area of the neural tissue is contained inside the cranium or skull. It is possible because of large number of infoldings which take the shape of sulci and gyri. The part which caves in is called the sulcus and the elevated part is called gyrus.

The weight of brain in an adult is approximately 1.4 kg and it appears as a soft structure. It is covered inside three coverings :  the outermost layer is called duramater, the middle layer is called Arachnoid layer and the innermost layer is Pia mater. In between Arachnoid and Pia mater there is a space called Subarachnoid space which contains Cerebrospinal fluid ( CSF ).Three membranes cover the brain and spinal cord, these are known as meninges. The Dura is also called the pachymeninx, and the arachnoid and pia are called the leptomeninges.  the dura mater is tough, fibrous sheath and is continuous with the spinal dura.

The arachnoid is a thin, transparent sheath separated from the underlying pia by the subarachnoid space, which contains cerebrospinal fluid ( CSF).

Brain floats inside a fluid called cerebrospinal fluid (CSF). CSF is contained between Arachnoid layer and Piamater.

Cerebral hemispheres, corpus callosum, brain stem , cerebellum are contained inside a hard bony structure known as cranium or skull. To protect the soft brain against the hard bony structures, there are wide CSF spaces at the base of the brain, known as CSF Cisterns.

Cerebral cortex on surface can be divided into four major lobes- Frontal, Parietal, Temporal and occipital Lobes.

The brain components can be understood in a very simple way as this picture. The large part above is called Cerebrum and posterior and lower part is called Cerebellum. Cerebrum consists of two cerebral hemispheres. Cerebellum is situated on posterior aspect of brain, below the cerebrum and behind brain stem. Brain stem comprises Midbrain, Pons and Medulla oblongata.

Each cerebral hemisphere can be divided into Frontal, Parietal , temporal and Occipital Lobe. The two cerebral hemispheres are connected in the midline  with a bundle of commissural fibers known as Corpus Callosum.

Spinal cord is the continuation of the lower part of brain stem, i.e., medulla oblongata. Medulla oblongata ends at foramen magnum, i.e., an opening at the posterior end of skull

This picture provides an idea about the three fossae of the inside of the cranium or skull. The anterior cranial fossa, middle cranial fossa and posterior cranial fossa.This picture is a diagrammatic representation of the view of the skull base as seen from above after removing the skull cap. One should learn to draw this simple yet a very important diagram. Locate the greater wing of the sphenoid bone, anterior clinoid procees, petrous bone, posterior clinoid process and foramen magnum in this diagram. Rest of the three diagrams are are enlarged view of the base of the three intracranial fossae.

 

A circle of arteries at the base of the brain providing major blood supply to the brain. It is named after the English neuroanatomist Sir Thomas Willis. It is formed by two anterior cerebral arteries which are in communication with each other anteriorly through one anterior communicating artery. There are two posterior communicating arteries which are connected to the posterior cerebral arteries, the terminal branches of basilar artery.

This image simplifies the concept of blood supply of the brain. Two Internal carotid arteries ( ICA) and two vertebral arteries supply the arterial blood to whole brain. About 85% of blood supply comes from ICA and it constitutes anterior circulation, remaining 15% comes from vertebral artery which contributes to posterior circulation

Basilar artery is formed by union of two vertebral arteries. Basilar artery runs just anterior to the Pons.

Vertebral artery passes through foramen transversarium of the cervical vertebrae. The transverse foramen or foramen transversarium is an opening in the transverse process of the cervical vertebrae. The foramen transversarium of 7th cervical vertebra is rudimentary. Foramen transversarium is an opening occupied by the vertebral artery and vein in the first six cervical vertebrae and only the vertebral vein in the seventh. 

Vertebral artery enters the cranium through the Foramen Magnum, from posterior to anterior. Two vertebral arteries join to form Basilar Artery in front of the Pons. Basilar artery runs in midline, anterior to the Pons.

This diagram shows the Circle of Willis, Optic Chiasma, Mamillary bodies and related structures.

All the veins of the brain drain into Internal Jugular Vein which drains into right atrium of the heart. But the venous drainage of brain is different from other structures of the body. The veins of the brain can be described as superficial and deep venous systems of the brain. 

In the mid sagittal section image: Below the corpus callosum is lateral ventricle and below the Fornix is third ventricle. The Floor of the third ventricle shows pituitary stalk. This picture gives an idea about the relation of the brain to the orbit, location of pituitary gland to the nasal cavity, location of the brain stem.

Following anatomical structures are seen on normal non-contrast CT scan of the brain:

CT scan findings in cases of CNS tuberculosis

NCCT scan of brain may be normal in the initial phase of TBM. CECT brain reveals abnormal meningeal enhancement, leptomeningeal enhancement at sylvian fissure, tentorium, obliteration of basal cisterns, basal meningeal enhancement (basal exudates), granulomas in the basal meninges and ependymitis, hydrocephalus, calcifications, ring enhancing granulomas, abscess and infarctions in the supratentorial brain parenchyma, cerebellum and brain stem.

CT features of tubercular meningitis (TBM)

 CT scan of Brain axial views: A. Non-contrast and B. with contrast,

showing meningeal enhancement and ventriculomegaly. 

A

B

The early changes in ventriculomegaly is suggested by the blunting of the frontal horns of the lateral ventricle. The temporal horns become visible and size becomes more than 2 to 3 mm. Third ventricle no longer remains slit like and becomes globular. The sulci become effaced in the obstructive hydrocephalus. Hypodensity in the brainstem on NCCT scan head could be due to infarct or edema in the brain stem.

NCCT Scan of head showing hypodensity in the Brain Stem

 Hydrocephalus in TBM can be of two types: (1) communicating type, which is common, secondary to an obstruction of the basal cisterns by inflammatory exudates and (2) obstructive type, which is less common and either secondary to a focal parenchymal lesion causing mass effect or due to the entrapment of a part of the ventricle by granulomatous ependymitis.

Periventricular hypodensity (PVL: periventricular lucency) on CT images is due to the seepage of the CSF fluid across the white matter and usually suggests hydrocephalus under pressure, which is an indication for CSF diversion surgery to decompress the ventricular system. 

 The common site of ventricular obstruction in obstructive hydrocephalus is aqueduct causing enlargement of the lateral and third ventricle. However, there may fourth ventricular outlet obstructon (foramen of Luschka and foramen of Magendie) leading to panventriculomegaly. Sometimes, there may be enlargement of only one ventricle.

 This is a sign of raised intraventricular hydrostatic pressure and raised intracranial pressure and indicates need for prescribing cerebral decongestants, including acetazolamide or necessitates some kind of CSF diversion procedure. In cases of TBM, periventricular hypodensity could also be due to spread of an inflammatory process.

The easy way to recognize ventriculomegaly on the CT is that there will be enlargement of the ventricular size, the frontal horns may look blunted; the third ventricle may become globular; the cisterns may get obliterated in case of obstructive hydrocephalus; the temporal horns of the lateral ventricle may look prominent and more than 2 to 3 mm in size.

CT findings in Vasculitis

The adventitial layer of small and medium-sized vessels develops changes similar to those of the adjacent tuberculous exudates. The intima of the vessels may eventually be affected or eroded by fibrinoid-hyaline degeneration. In later stages, the lumen of the vessel may get completely occluded by reactive subendothelial cellular proliferation. Ischemic cerebral infarction resulting from the vascular occlusion is a common sequelae of tuberculous arteritis. The middle cerebral and lenticulostriate arteries are most commonly affected.

 

                       CT scan Brain showing shunt in situ and diminished ventricle size.

On CT scan, tuberculoma may also appear as hypodense lesion with ‘out-of-proportion’ edema in cerebritis stage. Mature tuberculoma shows either ring or nodular enhancement with perilesional edema. Caseating tubercular granuloma on CECT shows a rim-enhancing lesion with a caseating hypodense center.

The “target sign” (central nidus of calcification surrounded by a ring of enhancement) indicates tuberculoma.

The radiographic presentation of tuberculoma depends largely on whether the lesion is noncaseating, caseating with a solid center, or caseating with a liquid center; with surronding edema. While new or enlarging tuberculoma may occur in some patients despite adequate ATT, the activity of tuberculoma can generally be assessed by the degree of contrast enhancement on follow-up CT .

 

Calvarial TB

             Contrast enhanced CT axial view  

    Post operative CT Scan: resolution of the lesion after surgery and completed course of ATT. 

Radiology of intracranial Tubercular Subdural Empyema

A 13 year old boy had presented with history of  seizures, headache , vomiting,  altered sensorium and weakness of right upper and lower limbs. He had 3 episodes generalized tonic clonic seizures ( GTCS) in last one month , fever , headache, vomiting, and  weakness of right half of body for last 7 days.  On examination, pallor was present and he was febrile, drowsy, irritable, and with right hemiparesis. 

 

CT scan of brain revealed left frontal convexity and anterior hemispheric fissure subdural space collection. CT scan of skull  with contrast left frontal interhemispheric. parasagittal subdural hypodensity in anterior falx region with perilesional edema and effacement of sulci and gyri in anterior frontal region with peripheral enhancing lesion in left frontoparietal region.

 

CT scan of brain with contrast showing intracranial multiple extraaxial  hypodense collections with peripheral enhancement with edema with gyral enhancement and mass effect

   At the time of bur hole surgery a thick pus came out after opening of the dura and patient was treated

successfully with anti-tubercular therapy (ATT).

ROLE OF CT GUIDED STEREOTAX

Streotactic procedure done with the help of CT scan helps in retrieving biopsy material from the deep located lesions in the eloquent area of the brain. It may be used either for the diagnostic or therapeutic purposes.CT guided stereotactic procedure helps in histopathological confirmation of the lesion which remains the gold standard to increase the diagnostic accuracy and to avoid inappropriate treatment . Stereotaxy may also be used for the aspiration of deep seated tuberculous lesion in brain not responding to conservative treatment and decision is warranted to start second line ATT after obtaining drug sensitivity testing of the pathological sample.

 Role of CT scan brain in patients of stroke

Stroke or cerebrovascular accident (CVA) is the suddeen onset neurological deficits in patients due to the involvement of the vascular supply of the brain . Stroke is of two types: infarct or hemorrhage. In such patients CT scan of the brain is the initial investigation. The intracranial bleed of hemorrhage is very claerly seen on CT scan of the brain as hematoma is more white or hyperdense as compared to the brain.

In cases of infarct CT scan of the brain shows hypodense area. If infarct is associated with mass effect with midline shift then decompressive craniectomy is done. A wide frontotemporoparietal craniotomy is made on one side of the cranium to reduce the intracranial pressure. It is commonly done in traumatic brain injury, middle cerebral artery ( MCA) infarcts. About 10-15% patients with MCA infarct suffer from progressive clinical detrioration due to increased brain swelling, raised intracranial pressure (ICP) and subsequent herniation. Such space occupying infarct is commonly referred to as malignant MCA infarct.

Per-operative photograph of the patient showing large bone flap beneath the scalp.

Non-contrast CT scan of the brain in which a large hypodense area is seen middle cerebral artery territory. Craniotomy defect is seen causing relif of the intracranial pressure as there is no midline shift and both lateral ventricles are normal in size. 

  

After craniotomy the bone flap is kept and preserved inside the abdominal wall  by making a pouch in the abdominal wall . A large fronto-temoporo-pariental free bone craniotomy of about 12 centimeter to 15 centimeter is elevated with lax duraplasty. The free bone is placed in the subcutaneous fat pocket in the right iliac region of lower abdomen inferolateral to the umbilicus. When patient improves and there is no evidence of midline shift or any intracranial mass effect , then cranioplasty is done with the same preserved bone to reconstruct the cranial defect.      

CT scan in head injury patients

These may occur under or opposite (contre-coup) the site of impact, but most commonly involve the frontal and temporal lobes.

Intracranial bleeding may occur either outside ( extrdural) or within the dura (intradural). Intradural hematomas are usually subdural and intracerebral.

Extradural hematoma ( 27%)

Subdural hematoma (26%)

Intracerebral hematoma +/- subdural ( 38%)

 

Brain edema/ cerebral edema/ herniations

Cerebral edema or brain edema or brain swelling may lead to tentorial or tonsillar herniations 

Efficient management prevents secondary brain damage through adequate oxygenation & maintenance of adequate cerebral perfusion pressure (CPP).

Improvement in prehospital care, advanced trauma life support and urgent CT scan of head injury patients improves the clinical outcome of  traumatic brain injury (TBI) patients.

Acute Epidural Hematoma or extradural hematoma (EDH) usually occurs due to rupture of the middle meningeal artery and bleeding from diploic spaces due to fracture of cranial bones

In such patients deteroration is very rapid, so if CT shows EDH of size more than 30 cc , craniotomy and evacuation of hematoma should be done as early as possible 

Acute SDH

Rupture of the bridging veins from the cortical surface.

Spontaneous Intracerebral Hematoma

Intracerebral hematoma (ICH) is the hemorrhage within the brain parenchyma

ICH accounts for 10% of all strokes

Risk factors: old age ( median age 56 years), long standing hypertension, diabetes, alcohol intake, smoking

Primary or secondary

Primary (80%): spontaneous rupture of small vessels damaged by chronic hypertension or amyloid angiopathy

In 1968, Charcot & Bouchard attributed ICH to rupture at points of dilation in the walls of small arterioles that they called microaneurysms.

 

Secondary ICH : vascular abnormalities (AVM, Cavernous angiomas), tumors, coagulopathy

Location: Basal Ganglia ( Putamen, Globus Pallidus 50%), Thalamus (15%), Pons (10%), Cerebellum (10%)

•      Common arteries involved is lenticulostriate branches of anterior & middle cerebral arteries which form Charcot-Bouchard microaneurysms 

CT scan: Hyperdense, volume can be measured,

CT angiography, MRI contrast, MR Angiography & Digital Substraction Angiography (DSA) is useful in secondary ICH.

Lobar hemorrhages are evacuated using craniotomy & corticectomy centered over the hematoma, with sparing of eloquent brain tissue