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.
MRI brain is an important neuro-imaging investigation. This is a non-invasive investigation in which no radiation is used. Unlike CT scan which utilizes X-ray no radiation exposure occurs in MRI so it is safe in pregnant ladies. MRI utilizes magnetic field.
In MRI, the soft tissue picture is better than CT scan. The anatomical details are better and it is multiplanar. Because different sections are obtained in MRI like axial, coronal and sagittal, it is multi-planar. In CT usually the axial images are obtained.
But MRI is more costly than CT scan and it is more time consuming. MRI machine also produces sound and some patients complain of claustrophobia. Steel or ferromagnetic foreign material like bullet metallic pellets, or implants are contraindicated for MRI. Bone and acute bleed or hemorrhage or hematoma appears white (hyperdense) in CT scan so fracture of the skull or intracranial bleeding is easily diagnosed on non-contrast CT scan of the brain. These issues make CT scan brain as investigation of choice for head injury patients. Only in few cases of head injury like diffuse axonal injury, MRI brain is required. Many patients of head injury want MRI brain but they should be told that whatever finding on neuroimaging in head injury warrants neurosurgical intervention in head injury patient, is very well diagnosed on non-contrast CT of brain ( NCCT brain).
On MRI Brain , structures which appear more white as compared to brain are labelled as hyper-intense. Intracranial lesions which show similar appearance on MRI as compared to brain are labelled as iso-intense lesions. The intracranial lesions which appear less white than brain on MRI brain are labelled as hypo-intense. Pneumocephalus contains air and appears more black as compared to brain and is hypointense. Similarly arachnoid cyst which contains CSF inside is a hypointense lesion on brain MRI T1 weighted image.
This diagram shows a lateral view of the face or brain or skull and the level A and B of cross sections. If image is taken at the level of "A" only two cerebral hemispheres will be seen . One can start reading the MRI brain from this level. This is usually the last image of axial view of MRI of the brain. At this level , it is very easy to identify the outermost hyperintense scalp fat 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. 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.
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.
The aial MRI brain imageat the level of basal ganglia is a 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.
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.
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.
Diagrammatic representation of 3 types of Sylvian fissure arachnoid cyts
Contrast MRI 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.
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. Hypointensity in the brainstem on MRI brain T1 weighted image and hyperitensity on T2 weighted image head could be due to infarct or edema 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 hypointensity (PVL: periventricular lucency) on T1 weghted MRI brain and hyperintensity on T 2 weighted image 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.
The easy way to recognize ventriculomegaly on MRI 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.
MRI findings in Vasculitis
On MRI brain, tuberculoma may also appear as hypointense lesion on T1 and hperintense on T2, with ‘out-of-proportion’ edema in cerebritis stage. Mature tuberculoma shows either ring or nodular enhancement with perilesional edema. Caseating tubercular granuloma on CE MRI shows a rim-enhancing lesion with a caseating hypointense center on T1 and hyperintense on T2 weighted image.
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 MRI .
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.
MRI brain revealed left frontal convexity and anterior hemispheric fissure subdural space collection. MRI 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.
successfully with anti-tubercular therapy (ATT).
Role Of MRI Guided Stereotaxy
Streotactic procedure done with the help of MRI machine 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. MRI 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.
Stroke or cerebrovascular accident (CVA) is the sudden 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.
Metastases most commonly spread via through hematogenous route. The brain parenchyma is the most common site (80%), followed by the skull and dura (15%). Direct extension to brain from a cancer of adjacent structures like cancers of nasopharynx, paranasal sinuses, middle ear (e.g. squamous cell carcinoma, esthenioneuroblastoma) is much less common than hematogenous spread . Diffuse leptomeningeal (pial) and subarachnoid space infiltrations are relatively uncommon, accounting for just 5% of all cases. Brain metastases are preferably located in arterial border zones and at the junction of cerebral cortex and subcortical white matter. Only about 3-5% occur in basal ganglia region. About 15% of metastases are found in the cerebellum. The midbrain, pons and medulla oblongata are uncommon sites and account for less than 1% of metastases. Other rare sites include the choroid plexus, ventricular ependyma, pituitary gland and retinal choroid. The metastasis may also occur through the CSF pathway and may present as drop metastasis. Primary brain tumors like germinoma and medulloblastoma may spread along CSF pathways. Some systemic cancer like lymphomas and leukemias involve leptomeninges and is known as meningeal carcinomatosis. It is a diffuse metastasis in the leptomeninges by carcinomatous infiltration.
This middle aged female had multiple intracranial metastses without detectable systemic primary cancer.
Intraoperative image shows defect in the cranial bone as seen after excision of the soft to firm swelling just beneath the scalp incision. Tumor was adherent to dura also. Intracranial lesion was mainly cystic with soft, suckable and moderately vascular surrounding solid compnent of the metastatic lesion.
For explaining functional fMRI in an easy and simple manner, it can be said that fMRI is similar to MRI in the sense that it involves MRI machine and produces scans similar to MRI except it highlights the "functional brain" area . It is based on the principle that when an area of the brain is in use, the blood flow to that region increases. So, the neuronal activity changes the blood flow ( Hemodynamic Response) and which, in turn, changes the magnetization between oxygen -rich and oxygen-poor blood. f MRI uses the blood-oxygen level dependent ( BOLD) contrast and maps the neuronal activity by imaging the changes in hemodynamic response of a brain area when a patient performs an activity.
When a person is told to perform some activity or a stimulus is received by a patient ( Paradigm) , the neurons corresponding to that functional area of the brain become active , local blood flow to those brain regions increases , and oxygen rich ( oxygenated) blood displaces oxygen- depleted ( deoxygenated) blood around 2 seconds later. his rises to peak over 4-6 seconds , before falling back to original level. Deoxygenated Hemoglobin (dHB) is more magnetic ( paramagnetic) than oxygenated Hb , which is virtually resistant to magnetism ( diamagnetic). This difference to magnetism can lead to an improved MR signal and which can be mapped to show which neurons are active at a time.
Neurosurgeons may use fMRI for pre-surgical planning for lesions close to eloquent area of the brain, e.g., motor area. Similarly , language , memory areas can be mapped.
fMRI had also been used in research, effect of stroke, brain injury on brain functions , effect of drugs, lie-detection, etc.
Event related design involves individual events rather than blocks, and can be randomly distributed during the study.
MRI spine has revolutionized the diagnosis of spinal cord lesions. MRI spine is the investigation of choice for spinal cord injury. For many decades myelogram was the only investigation for the diagnosis of spinal cord lesions and it provided an indirect evidence of the spinal cord lesion. It was an invasive investigation and required injection of contrast through lumbar puncture. But, MRI spine directly visualizes the spinal cord and can easily diagnosed extradural, intradural and intramedullary lesions. Ability of MRI machine to obtain sagittal image has greatly benefitted the patients. Sagittal and axial images along with different sequences ( T1, T2, FLAIR, etc) help in making he diagnosis with great ease. So, now a days it is very rare to see myelogram, as CSF space around the spinal cord is seen in MRI of the spine. The CSF in thecal sac around the spinal cord appears hypointense on T1 weighted image and hyperintense on T2 weighted image.
The MRI spine shows vertebrae, intervertebral discs, ligaments, spinal cord and other adjoining anatomical structures.
The spinal cord lesions can be extradural, intradural -extramedullary and intramedullary lesions.
Intramedullary tumors are the tumors which are present in the spinal cord, i.e., inside the pial covering and substance of the spinal cord itself.
Intradural Extramedullary (IDEM) tumors are mainly neurofibroma and meningioma.
Intradural intramedullary lesions comprise 20 to 30% of all primary spinal cord tumors.
Gliomatous and nongliomatous tumors constitute 90 and 10% respectively.
In 75% cases, the astrocytmas extend over 4 or less 4 vertebral segments. In some cases the lesions extends throughout the spinal cord, for example holocord astrocytomas.
Half of the central nervous system ependymomas are located in the spinal cord and, of these, 50% are located in the filum terminale. The next common site is the cervical cord.
Glioblastomas are not common.
Hemangioblastoms are rare, consist of less than 2% of primary spinal cord tumors.
Clinical presentation depends upon the site and size of the lesion.
MRI of spine with contrast is the investigation of choice.
The operating microscope, bipolar coagulators, intraoperative physiological monitoring ( somatosensory evoked potenial monitoring, motor evoked potential ) , microscissors, microdissectors, small tumor holding forceps, Cavitron Ultrasonic Surgical Aspirators (CUSA) , intraoperative USG ( Ultrasonography) are good for safe excision of intramedullary lesions.
Spinal dysraphism means a spectrum of congenital anomalies of the spine and spinal cord.
Spina bifida is a common form of spinal dysraphism. The term spina bifida includes a wide variety of anomalies.
Congenital defect in the spine leads to spina bifida. This can be of two types: spina bifida occulta and spina bifida aperta.
In spina bifida aperta; visible lesion, like a swelling over the midline of the back may be noticed at the time of birth of a child. Such spinal dysraphism is known as Spinal Bifida Aperta.
But, a child may be having some abnormalty of the spine or spinal cord but without any externally visible lesion and overlying skin is intact, then it is known as Spina Bifida Occulta. This defect of the vertebrae of the spine of a child may not be visible at the time of birth and there may be no visible exposure of meninges or neural tissue. And, there may be congenital defect only in the lamina of the vertebrae of the spine without any involvement of underlying spinal cord. This is known as spine bifida occulta.
But, in spina bifida aperta there is a visible or open defect in the spine. There may be congenital defect in vertebral arches with cystic distension of meninges which is filled with CSF and is known as Meningocele. If, in this congenital defect of the vertebral arches there is a cystic dilatation of meninges and cerebrospinal fluid along with neural tissue or spinal cord ( Myelon) , then it is known as Myelomeningocele. If Myelomengocele contains fat tissue, then it is known as Lipomyelomengocele.
Myelmeningocele is one of the congenital open neral tube defect present at the birth on the back of the newborn.
It is a common type of congental defect of the spine and its incidence is about 1 in 1,000 live births. Better nutrition and folic acid suplementatiion during the antenatal care of the mother decrease its occurrence.
Ultrasound study during the early antenatal care detects any occurrence of myelomeningocele in a fetus during pregnancy.
A newborn child should be assessed for any sensory or motor deficit due to meningocele or myelomeningocele. There may be associated congenital lesions, like cardiac lesions. Myelomeningocele may be associated with congenital hydrocephalus. So, MRI of the spinal cord and brain is investigation for choice for assessing a case of meningcele. MRI may show whether a swelling on the back of a child is only flled with CSF or does it contain any neural tissue. It detects any intraspinal extension, associated intrasinal dermoid, lipoma, dermal sinus, spina bifida, spinal dysrahism like duplication of the cord, any bony spur between the duplicated cord, Chiari malfomation, syrinx, hydrocephalus, thickened filum terminale, etc. So, MRI helps in diagnosis, surgical planning and predicting prognostic outcome.
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