Clinical and practical knowledge of Intracranial Pressure (ICP) & Cerebral Perfusion Pressure (CPP)

 Quincke in 1891 first reported the measurement of intracranial pressure through lumbar route.

Quickenstedt  established the range of normal ICP and demonstrated the effect of changes in body position and respiration .
Lundberg, in 1960, described the 3 ICP waveforms.
Cranium is like a rigid bony sphere with a constant intracranial volume and it contains three components

1. Brain    1400 mL

2. CSF       150 mL

3. Blood    150 mL

Therefore, any change in the volume of the brain causes a reciprocal change in the volume of other intracranial components,i.e., either blood or CSF.  This is the basis of Monro-Kellie hypothesis introduced in neurosurgery by Cushing.

There is a relationship between  intracarnial volume and intracranial pressure.  Because cranium  is  a rigid and non-distensible structure, any increase in the volume of a component would be accompanied by a reciprocal decrease in the volume of the other two components. Once the volume buffering capacity is exhausted, the ICP would begin to rise.

During gradual expansion of a mass lesion, the volume displaced may be CSF, intravascular blood or brain tissue water. Of the three components, CSF appears to be the main buffer and is the first to be displaced as evident  by compressed ventricles  and obliterarted subarachnoid spaces.

The rate of expansion of an intracranial mass is also important. A rapidly growing intracranial mass lesion may outpace the compensatory shift of CSF and even the smallest increase in mass could produce a life threatening increase in ICP. Thus, a large hematoma could be accommodated within a few hours without dangerous rise in ICP.

Intracranial hypertension can lead to secondary changes by interfering with the cerebral blood flow ( CBF). The normal  cerebral blood flow ( CBF) is about 50 mL/100 g/min.

Cerebral Perfusion Pressure ( CPP) is defined as the difference between mean arterial pressure

( MAP) and intranial pressure (ICP).

CPP= MAP-ICP

Normal range of ICP in an adult is less than 10-15 mmHg.

Cerebral perfusion pressure is normal till the autoregulation mechanism of brain is intact. But there is a range upto which level body is able to maintain CPP.  Between 60 to 160 mmHg of mean arterial pressure brain will be able to receive blood with normal perfusion. But, if MAP falls blow 50 mmHg, features of cerebral ischemia will appear.
Mean Arterial Pressure ( MAP)= Diastolic Pressure+1/3rd of Pulse Pressure 
Pulse pressure= Systolic blood pressure - Diastolic pressure
So, in a normal person MAP = 80 mmHg+ (120mmHg-80mmHg)/3
MAP= 80+40/3
So on average, roughly MAP is about 90-95.

A rise in ICP would lead to a fall in CPP unless buffered by a compensatory rise in blood pressure ( Cushing response). Raised ICP can cause hypertension, bradycardia and respiratory changes. Therefore any patient who is suspected as a case of intracranial space occupying lesion ( ICSOL), like brain tumor or hematoma or granuloma or abscess and complaining of headache, vomiting, blurring of vision then blood pressure and pulse rate should always be monitored. In clinical setting bradycardia is a reliable indicator of rise in ICP in a patient who was otherwise allright sometimes back. Bradycardia is a sign of raised ICP and can precede and ppears before deterioration of conscious level ( Drowsinees, disorientation or poor Glasgow Coma Scale) and papillary asymmetry.

Lundberg described three pressure waves namely A waves, B waves and  C waves .

A waves
A waves are pathological  and indicate rapid rise in ICP  for variable period and then rapid fall to the baseline.
The A waves that persist for longer periods( usually 5-20 minutes) are called plateau waves.
Smaller A waves termed “ atypical” or “ truncated” A waves , that often do not exceed an elevation of 50 mm Hg, are also clinically important early indicators of neurological deterioration.

The A waves are accompanied by clinical features  of raised ICP, like headache, vomiting, decerebrate posturing, papillary changes, bradycardia and hypertension and respond to CSF drainage, hyperventilation and osmotic diuretics.

B waves

Occur at the rate of 0.2-2 per minute and are related to respiration.

B waves may be vasomotor in origin. Lundberg initially described them in patients with intracranial hypertension, though they can occur in normal individuals.
B waves are said to be one of the best predictors of outcome after surgery for normal pressure hydrocephalus.

C waves

C waves are low amplitude with afrequency of 4-8 per minute. These waves are thought to be related to Traube-Hering- Mayer waves.
C waves are of little clinical significance.

There is pressure equilibrium in the skull  but if pressure rises then a part of brain herniates. The herniations are subfalcine, tentorial, and tonsillar. In subfalcine herniation, a part of the frontal lobe herniates below the falx to the opposite side . In tentorial herniation ( Uncal herniation) a part of the medial temporal lobe herniated below through an opening in the tent and compresses over the midbrain. In tonsillar herniation, a part of cerebellum,i.e, Cerebellar Tonsil herniates down through the Foramen Magnum and compresses the medulla oblongata ( Coning). Brain Herniation is life threatening as it causes  brain stem compression which contains vasomotor center. Patient presents with drowsiness, deceerbrate posturing, papillary asymmetry, bradycardia, hypertension and respiratory irregularities.

Increased ICP is indicated by a sustained elevation in pressure above 15 mmHg or when intermittent A or B waves are recorded.

The normal CSF pressure measured through the lumbar route ranges from 50 to 200 mm H₂O in the lateral decubitus position.

ICP and CPP monitoring are important in the management of head injury patients, especially in whom the decision to operate is equivocal. Surgery may be required if ICP is progressively rising and not responding to conservative treatment with cerebral decongestants. ICP monitoring may also be required in patients of spontaneous subarachnoid hemorrhage (SAH) to assess the effect of cerebral vasospasm and in patients of arrested hydrocephalus and  normal pressure hydrocephalus to take decision about CSF diversion procedure.

Various methods of monitoring the ICP

1.       Intraventricular catheters like External Ventricular Drainage ( EVD): Most accurate, lower cost, also allows therapeutic drainage of CSF

2.       Intraparenchymal catheters (eg. Camino labsor Honeywell/Phillips)

3.       Epidural catheters ( e.g. Fibreoptic tipped catheter: Ladd fireoptic)

4.       Subarachnoid bolt (screw)

5.       Subdural ( eg. Cordis Cup catheter)

Monitoring Systems can broadly be divided into Fluid coupled system and Non-fluid cupled system

In fluid-coupled system a fluid filled catheter or a hollow bolt placed in the ventricle, subarachnoid space or the subdural space connected to a pressure transducer through a fluid-filled line. The transducer converts the hydraulic pressure into an electrical signal which can be displayed  digitally or an oscilloscope.

In Non-fluid coupled systems, the transducer is mounted on the monitoring device itself.

In infants and in children below 18 months of age , the anterior fontanelle is open. Tense anterior fontanelle indicates raised ICP and intraventricular pressure. CSF drainage can be done from the right side lateral angle of the diamond shaped anterior fontanelle.

In clinical setting  cerebral edema is one of the important causes of raised ICP.  if a patient presents with clinical features of raised intracranial pressure, then following steps may be helpful:

Bed rest  reduces the cerebral  metaboloic  rate of oxygen consumption and decreased blood supply

Oxygenation

Elevation of head end of the bed to 30^o

Acetazolamide ( Diamox tablet) is a carbonic anhydrase inhibitor and is available in tablet form . In an adult 250 mg tablet can be given orally three times a day( tds)

Frusemide or Furusemide ( Lasix) is a loop diuretic and is available in both oral and injectable form. A dose of 40 mg twice a day reduces the cerebral edema ICP. But Frusemide use may cause  potassium  loss leading to hypokalemia so serum electrolyte monitoring should also be done. To avoid hypokalemia , potassium supplement is advised for example syp Potklor  1 TSF twice a day or Injection KCL  in Intravenous  infusion may be given. Another drug can be prescribed is Spiroolactone( Lasilactone), a potassium sparing diuretic and then potassium supplementation is not required.

Injection Mannitol 100 ml stat or 100 ml 8 hourly ( 1 -1.5 Gm/ kg body weight in divided doses in an adult) for three days and then Syp Glycerol 6 TSF three times a day for about 2 weeks.

Dexamethasone 4 mg 6 hourly in injectabe or oral form. Ranitidine or other antacid should be prescribed alog with steroid to avoid gastritis. Dexamethasone is diabetogenic and raises blood sugar level. Prolong  use is associated with fluid retention and swelling over face and body.

CSF drainage is another way to reduce ICP. Ventricular tap is done usually through the point just anterior to the coronal suture on right side , about 3 cm lateral to the sagittal suture . This is a ethod of reducing ICP in a patient with post meningitic hydrocephalus and at the time of surgery. And if CSF pressure is persistently high then External ventricular drainage system can be used.

Elective hyperventilation is a mode or reducing ICP. Hyperventilation leads to CO₂ wash out which  causes vasoconstriction and decreased blood supply to the brain leading to decreased ICP. In this procedure patient is intubated after giving muscle relaxant and put on ventilation for about 48 hours. The ventilator mode is Controlled Mechanical Ventilation ( CMV) the respiratory rate is low,i.e., about 16/minute and monitoring of the patient is done with arterial blood gases(ABG) in which the pCO₂ is about 25mm Hg ( Normal range of arterial partial pressure of Carbon Dioxide ranges from 25mm Hg to 42 mmHg). Elective hyperventilation is often advise in patients with severe head injury, diffuse axonal injury, in a patient of spontaneous subarachnoid hemorhhage ( SAH) presenting with features of vasospasm, after a prolonged surgery with brain swelling during surgery.

Some surgical ways of reducing ICP are CSF diversion procedures ,  decompressive craniectomy or excision of the intracranial space occupying lesion( ICSOL) like hematoma, tumor or abscess.

Sources: 

Chapter 6. Intra-operative monitoring written by Babu KS, Rajsekhar VRamamurthy & Tandon’s manual of Neurosurgery ,  Editors:  PN Tandon, Ravi Ramamurthy, Pradeep Kumar Jain N, first edition: 2014 ISBN 978-93-5152-192-1

Handbook of Neurosurgery, Mark S Greenberg, 7^th edition ( Thieme Publishers)

Vascular Neurosurgery

William Harvey Cushing, Walter Dandy, Krayenbuhl, Yasargil, William Spence, Rhoton
Drake, Fredric B. Meyer, Michael T Lawton: Author of 'Seven Aneurysms-Tenets & Techniques for Clipping', Spetzler, Sugita, Dolenc, van Loveren, Hunt and Hess, Laligam Shekhar, etc have made important contributions.

Austrian physicist Christian Doppler (1842): described Doppler effect which led to  Doppler Ultrasound. The use of Doppler ultrasound to measure cerebral blood flow was initially reported by Satomara in 1959. Aslid & colleagues first reported the ability to record blood flow velocity in the intracranial arteries with Doppler ultrasound in 1982 and introduced TCD (Trans Cranial Doppler ) ultrasonography. The lower 2-MHz frequency allowed penetration through the cranium in the thin portions of the skull.

Kety and Schmidt ( 1948) applied Fick's principle ( Latter half of 19th Century) to  determine  Cerebral blood flow ( 54 ml/100 g per minute). Sundt noted that a minimal CBF of 18 mL/100 g per minute is needed to maintain a normal EEG parameters during carotid endarterectomy ( CEA).
Irreversible cellular damage occurs when CBF is below 10 mL/100 g per minute.

For treating carotid occlusive disease, the options include CEA, carotid artery angioplasty & stenting. William Spence performed the first successful performed Carotid endarterectomy (CEA) in 1951.


The most common cause of SAH is trauma.
Spontaneous subarachnoid hemorrhage due to ruture of intracranial aneurysm commonly occurs in the age group of 40-60 years with a peak incidence in the fifties.
Aneurysm bleed is the commonest cause of spontaneous SAH ( about 85%).
Other common causes of spontaneous SAH are:  artriovenous malformations ( AVM), hemorrhage from tumor, pituitary apoplexy, vasculopathy ( like collagen vascular disease, amyloid angiopathy , arterial dissection) , haematological ( anticoagulant therapy, leukaemia, hepatic or renal disease induced coagulopathy ) and drugs like cocaine, amphetamine and ephedrine.

Subarachnoid hemorrhage (SAH) is a neurological emergency  characterized by hemorrhage into the subarachnoid space, and may present as sudden, severe headache ( as bolt from blue ) which patient may state that he or she may have never experienced before. Sentinel hemorrhage occurs in about 40% of patients with SAH. This is also known as " warning leak". Nuchal rigidity or meningismus is noted in 50% of patients due to meningeal irritation following SAH. Hemiparesis, focal neurological deficits including cranial nerve deficits are other common features. Fundus examination may reveal papilloedema and subhyaloid hemorrhage.

On the basis of GCS and Focal deficit, the severity of the clinical presentation of the patients may be graded into 5 grades , according to the World Federation of Neurological Surgeons  (WFNS).
In WFNS Grade 1 the patients are of GCS 15/15 and have no focal deficit. And, if patient's GCS is 13 or 14 then it is Grade 2. And patient has a focal deficit with a GCS of 13 or 14, his grade becomes Grade 3.   poor GCS of 7-12 makes a patient of grade 4 and if patients GCS is 6 or less then his garde becomes 5, irrespective of the presence or absence of focal deficit.

NCCT ( NECT) , i.e., Noncontrast or nonenhanced CT scan of the barin is the first investigation of choice. It shows hyperdensity in the subarachnoid space and may indicate the site of bleed. or example, anterior communicationg artery aneurysm bleed shows blood or hyperdensity in the anterior interhemispheric cisterm. the ruture of the Middle cerebral artery may present with hematoma in the temporal lobe or in the sylvian fissure of that side.

Fischer's grading of SAH on the basis of CT findings:
In Grade 1: there is no detectable blood on CT scan
Grade 2 : Diffuse thin  SAH  less than 1 mm thickness, & if thickness of clot is more than 1mm then it is labeled as Grade 3.
Grade 4: Intraventricular or intracerebral clot with diffuse or no subarachnoid hemorrhage

If  CT scan is normal and still there is strong suspicion of SAH, then the next  investigation is Lumbar Puncture, which reveals xanthochromia.

Common locations of intracranial aneurysms include Anterior communicating artery ( 30%), the junction of the ICA and Pcom ( 25% ), MCA bifurcation ( 20% ), ICA bifurcation ( 7.5%). Around 7% arise from the basilar bifurcation and 3% arise from the PICA, a branch of vertebral artery.

Digital Substraction Angiography ( DSA) or CT Angiography ( CTA) is the investigation of choice. MR angiography ( MRA) does not use any contrast and it is a good non invasive screening investigation.
Trans cranial Doppler ( TCD) detects vasospasm.
Rebleeding is the major concern during the initial treatment of patients who are admitted with rupture of intraqcranial aneurysmal rupture. Hydrocephalus, seizure, neurological deficit due to vasospasm and ischemia are other common problems.
Vasospasm is treated by triple H therapy ( induced hypertension, hypervolemia and Hemodilution) to improve cerebral perfusion. Calcium channel blocker- Nimodipine in the dose of 60 mg four times a day is neuro protective. Intraarterial papaverine is also used as vasodilator for spastic arteries after SAH.
Clipping of the aneurysm and coiling of the aneurysm are the two options for treating intracranial aneurysms. Subarachnoid space is the arena of aneurysm surgery because it houses the brain's arteries & provides a navigable labyrinth to deep targets that can be dissected without violating or harming the brain. Subarachnoid dissection, therefore, is a foundation of vascular neurosurgery.
Posterior circulation aneurysms, multiple aneurysms, Poor grade patients or surgically unfit patients, aneurysms with AVM are indications for endovascular treatment with coiling.

Every intracranial saccular aneurysm is associated with a cistern:

    Middle cerebral artery ( MCA) aneurysm is in sylvian cistern
    Posterior communicating artery ( PCoA) & ophthalmic artery ( Oph A) aneurysm in carotid cistern
    Anterior communicating artery (ACoA) in lamina terminalis cistern
    Pericallosal artery (Pca A)  in callosal cistern
    Basilar bifurcation in interpeduncular cistern
    Posterior inferior cerebellar artery ( PICA ) in lateral cerebellomedullary cistern

The pathway to some aneurysm traverses several cisterns:

    For example, the pathway to Anterior communicating artery aneurysms progresses from carotid to chiasmatic to lamina terminalis cistern, & the pathway to basilar bifurcation aneurysms progresses from Slvian to carotid to lamina terminalis to crural to interpeduncular cistern.

So, arteries define a trail through the center of the subarachnoid space ( SAS). Every artery has a safe surface to follow during subarachnoid dissection. Safe surface means smooth contours and few branches. For example, the superior surface of the M1 MCA segment gives off lenticulostriate arteries, & dissection along this surface can injure them. In contrast, the inferior surface gives rise to anterior temporal artery which is easily seen and less vulnerable.

Careful subarachnoid dissection does not require division or sacrifice of even a small arterial branch. It can be mobilized if required.

Subarachnoid dissection remains " outside " of the brain so respect & preserve the pial boundaries outside of the vessel.

Skull base approaches minimize the brain retraction.

Pterional approach involves fronto-temporal craniotomy. Orbitozygomatic approach enhances the surgical exposure of standard pterional craniotomy.

Anteror interhmispheric approach is used to clip aneurysms of the pericallosal artery.

Far- Lateral approach or lateral suboccipital approach is needed for aneurysms of posterior fossa.

Sources;
Excerpts from
Seven Aneurysms Tenets and Techniques for clipping. Author : Michael T. Lawton ( Thieme) , 2012

Brain hemorrhage, Stroke or Cerebrovascular accident ( CVA) or Brain attack or Paralysis

The term "Heart attack" is very common used term and well understood by common people for a condition in which heart is affected and patient requires urgent medical treatmnt. Similarly in stroke, blood supply to the brain is affected and patient requires urgent medical attention.  

The brain is critically dependent on an uninterrupted supply of oxygenated blood. About 18% of the total blood volume in body circulates in the brain, which accounts for about 2% of body weight. Loss of consciousness occurs in less than 15 seconds after blood flow to the brain has stopped, and irreparable damage to the brain tissue occurs within 5 minutes.

Cerebrovascular accident or cerebrovascular disease or stroke occurs as a result of vascular compromise or hemorrhage and is one of the most frequent sources of neurologic disability.
Abrupt onset of Neurologic deficit is caused by inadequate perfusion of a region of brain.

Stroke is a common cause of neurological disability and death in elderly persons. Arterial thrombosis with occlusion of the cerebral arteries is the most common cause of stroke.

Most common modifiable risk factors are hypertension, cigarette smoking, obesity, increased blood lipids, heavy alcohol consumption, poor control of diabetes mellitus, stress, etc.

TIA ( Transient ischemic attack)
            Episode of focal neurological dysfunction as a result of ischemia which resolves completely within 24 hours.
            TIA are important determinant of stroke. around 30-50% of cases had previous transient ischemic attacks.

STROKE or CVA

About 85% of strokes are Ischemic and 15% Hemorrhagic.

HEMORRHAGIC STROKE
About 20% of strokes are hemorrhagic which is due to the spontaneous intracerebral hematoma (ICH). Hemorrhage most commonly results from rupture of the small penetrating arteries damaged by the degenerative effects of chronic hypertension.. In 1868, Charcot and Bouchard described the rupture of " microaneurysms" as the cause of ICH.

Common cause of spontaneous intracerbral hematoma in elderly is hypertensive bleed. As commonly seen in elderly that there is unnoticed hypertension in many elderly persons who are not aware about this condition or on irregular treatment of hypertension. Common site of hypertensive bleed is basal ganglia. 
So, the commonest cause of spontaneous intracerebral hematoma in adults is a hypertensive arteriosclerotic basal ganglionic bleed. The median age of spontaneous intracerebral hemorrhage is about 56 years.The common clinical features are sudden onset severe headache, vomiting, slurring of speech, depressed level of consciousness and weakness of face and limbs. 
Commonest cause is long standing hypertension, irregular antihypertensive medication, history of smoking and alcohol intake, diabetes and lack of physical exercise. 
CT scan of brain is the initial investigation.  

Basal ganglia ( Putamen, globus pallidus, caudate nucleus) is the commonest site of the hypertensive intracranial bleed.

Fibrous Dysplasia

 Fibrous dysplasia is usually a benign condition in which normal bone is replaced by fibrous connective tissue ( malignant transformation occurs in less than 1%). Most lesions occur in the ribs or craniofacial bones, especially maxilla.
Anatomical patterns may be Monostotic: most common,Polyostotic: 25%, & as part of McCune-Albright sdyndrome.
Clinically it may present as incidental finding, local pain, local swelling, pathologic fracture, cranial nerve compression
Fibrous dysplasia consists of proliferative connective tissue, causing thickening of bones.
There are 3 forms: Compact form, Lytic form and Pseudo pagetoid form.
1. Compact form is a dense thickening of bone , especially of the skull base, resulting in ground glass appearance. It may cause stenosis of the optic foramen , superior orbital fissure,  shallow orbits with proptosis, sellar and sphenoid involvement causing hypopituitarism and expansion of the temporal bone and greater wing of the sphenoid.
2. Lytic form takes the shape of a radiolucent area limited by a thin sclerotic line.
3. Pseudo pagetoid form is characterized by a combination of both sclerotic and  radiolucent lesions. The lesion stabilizes after the age of 25-30. There is a small risk of malignant transformation.


Investigation: Rraised serum alkaline phosphatase level,X Ray, CT scan & MRI.
Treatment of calvarial kesions: curettage and cranioplasty.

Sources: Manual of Neurosurgery,  Ramamurthy & Tandon, (jaypee publishers)
               Handbook of neurosurgery Greenberg, 7th ed ( Thieme) 

Coma and Glasgow Coma scale

Most of the non medical people use word coma to describe a patient who is unconscious. But for a medical professional word "coma" is very specific because the impairment of arousal can vary from drowsiness ( sleepiness) to non-responding to any stimulus like sound or pain. Coma is the severest impairment of arousal, and is defined as the inability to obey commands, speak, or open  the eyes to pain.

One should learn the GCS scale to better understand the different levels of impairment of conscious level and to avoid descrepencies in describing the daily condition of the patient by different medical professionals and nurses.
Teasdale and Jennet,  in year 1875,  proposed a scale known as GCS ( Glasgow Coma Scale). Three types of stimulus and response to the patient to these three stimuli is described.
First is EYE OPENING
If patient opens his eyes spontaneously , i.e., like a normal person without any problem , then 4 point is mentioned.
Next situation is that patient is drowsy or feeling sleepy and is having closed eyes. The sleepy patient if opens eyes on sound then 3 point is given.
If patient eyes are closed and he opens eyes only when painful stimulus is given the, only 2 points is given.
And patient does not open eyes even on a painful stimulus then only 1 point is given so the lowest score of eye opening is 1.

E  4   spontaneous eye opening
E  3   opening eyes to speech
E  2   opening eyes to pain
E  1   None


Then  patient's verbal response is examined ( V stands for verbal response)


 V   5         Person is oriented 
                 (aware about what is happening around, Person is oriented to place, person and time )
 
 V    4        Confused or disoriented  

 V    3       speaking inappropriate words 
                                      ( Not producing sentences )

 V    2       producing incomprehensible words 
                                       ( Not producing word i.e. only some sound is produced by the patient) 

 V    1      None ( No verbal output means patient is not speaking and even not producing any sound)


Patient's Motor response is assessed

M      6      Obeys
          (Best motor resonpse is  M6 when patients moves limbs themselves and obey the command to move hand and feet whenever asked to do so)

M     5    patient localizes pain 
           ( when patient is pinched he tries to remove your fingers) 

M    4    Withdraws to pain
            ( here when patient is pinched feels pain and tries to withdraw from the pain)

M    3    Flexion to pain ( decorticate)
             ( in medical terminology it is known as decorticate posture , i.e., posture seen in an animal when the central nervous system is cut just below the level of cerebral cortex. Like in an experient by Sherrington, father of modern neurophysiology, when the brain of a cat was cut just  above the midbrain or brain stem, animal,s upper limbs were flexed and lower limbs were extended. This abnormal posture is known as DECORTICATE POSTURE)

M    2   Extensor ( decerebrate )
               ( extensor response to a painful stimulus is a very bad neurological sign. When a patient is pinched his both upper and lower limbs are extended)

M    1  No response to the painful stimulus


The best responses of the patient are added . So, the maximum GCS score is 15 and minimum is 3.

 
Glasgow coma scale score of equal or less than 8 is a generally accepted operational definition of coma.
It can result from dysfunction of brain stem, diencephalon or lesions of both cerebral hemispheres.This may be due to neoplastic lesions, electrolyte imbalance, metablic or endocrine problems, vascular lesions, infections, trauma or nutritional reasons.

GCS is an important method of describing patient's neurological condition but blood pressure, pulse rate,  respiratory rate, response of the pupils of  eye to light, paralysis of the limbs are other important parts of the  complete neurological assessment.

Pilocytic Astrocytoma and Pilomyxoid Astrocytoma

Pilocytic astrocytoma  is a relatively circumscribed, slowly growing, and is  often cystic lesion.
It commonly occurs in in children and young adults.
It is histologically characterized by a biphasic pattern with varying proportions of compacted bipolar cells associated with Rosenthal fibers and loose -textured multipolar cells associated with microcysts and eosinophilic granular bodies.
Rosenthal fibers are intracytoplasmic  corkscrew-shaped, brightly eosinophilic, hyaline masses.
Pilocytic astrocytoma corresponds to WHO grade1. Pilocytic astrocytomas comprise approximately 5% of all gliomas. It is the most common glioma in children, in whom the majority ( 67%) arise in the cerebellum.
Preferred sites include the optic nerve, optic chiasma/ hypothalamus, thalamus and basal ganglia, cerebral hemispheres , cerebellum and brain stem.
Involvement of the subarachnoid space is a common finding in pilocytic astrocytoma. It is not indicative of aggressive or malignant behavior, nor does it pretend subarachnoid dissemination.
Pilocytic astrocytoma may also seed the neuraxis.
Pilocytic astrocytomas are remarkable in maintaining their WHO grade I status over years and even decades. Very rarely, especially when previously irradiated, a malignat transformation may occur.
As with other CNS lesions, the neurological sign and symptoms depend on the location and size of the tumor. similarly non localizing signs like macrocephaly, headache, endocrinopathy are also seen. Seizures are uncommon since the lesions infrequently involve the cerebral cortex. Visual loss, hypothalamic and pituitary dysfunction like obesity and diabetes insipidus may occur.
CT scan brain  with contrast or MRI brain with contrast with MR spectroscopy helps in preoperative provisional diagnosis of the lesion. The cysts may be either solitary and massive , the tumor being a mural nodule, or multiple, smaller and intratumoral.

Pilomyxoid Astrocytoma

A piloid neoplasm, closely related to pilocytic astrocytoma, that has a prominant mucoid matrix and angiocentric arrangement of monomorphous, bipolar tumor cells, without Rosenthal fibers  or eosinophilic granular bodies/ hyaline deposits. Pilomyxoid astrocytoma corresponds to
WHO Grade II neoplasm. It typically presents in very young age group , median 10 months.



 

Primary Central Nervous System Lymphoma ( PCNL)

Extranodal malignant lymphomas may arise in the CNS in the absence of lymphoma outside the nervous system at the time of diagnosis. it is different from secondary involovement of the nervous system in systemic lymphomas.
Primary CNS lymphomas ( PCNL) were first described by Bailey in 1929 as "perithelial sarcoma."
Primary CNS lymphoma constitutes about 3% of all brain tumors.
Most are large B-cell lymphomas , only 2% of T-cell origin.
PCNL affects all ages, with a peak incidence in immunocompetent subjects during the sixth and seventh decade of life.
In immunocompromised patients, the age at manifestation is lowest in individuals who have an inherited immunodeficiency ( 10 years ) , followed by transplant recipients ( 37 years ) and AIDS patients ( 39 years ).
Common location is the brain parenchyma surrounding the ventricular system, but any craniospinal structure can be involved. AIDS epidemic led to increase in the incidence of Lymphoma.  The  clinical manifestations are similar to other intracranial space occupying lesions of the brain and like other brain tumors CT scan and MRI with contrast and MR spectroscopy helps to diagnose these tumors.
Majority of patients present with focal neurological deficit. Some patients present with features of raised intracranial pressure like headache and vomiting. Few patients present with neuropsychiatric symptoms and seizures. Eye symptoms due to uveitis or vitreous lymphoma may occur in about 5 percent cases. Dementia may also be a symptom of cns lymphoma.
About 50% of transplantation associated primary cns lymphomas appear within a year after transplantation.
PCNSL occur as a single or multiple masses in in deep location in cerebral hemisphere or in the peri ventricular region. It may be diffuse or well demarcated. Diffuse infiltrative form may present as lymphomatous cerebri. Meningeal lymphoma may present as meningioma or meningitis.
On CT scan it is infiltrative lesion with indistinct margins and isodense or hyperdense with homogeneous enhancement with minimal surrounding edema or compressive effect.  Solitary lesion in majority of cases. Lesions are usually supratentorial and localized in the deep periventricular areas.
Clinical presentation is similar to any other space occupying lesion. Steroid , cerebral decongestants and antiepileptic medication are given and a tissue diagnosis is possible with open biopsy and stereotactic biopsy.

2016- World Health Organization (WHO) classification of CNS tumors has classified the Lymphomas of the central nervous system as follows:

Diffuse large B-cell lymphoma of the CNS

Immunodeficiency-associated CNS lymphoma

          AIDS-related diffuse large B-cell lymphoma

          EBV-positive diffuse large B-cell lymphoma, NOS

          Lymphomatoid granulomatosis

Intravascular large B-cell lymphoma

Low-grade B-cell lymphoma of the CNS

T-cell & NK/T cell-lymphoma of the CNS

Anaplastic large cell lymphoma , ALK-positive

Anaplastic large cell lymphoma , ALK-negative

MALT lymphoma of the dura

Source: WHO classification of CNS tumors, 4th Ed. 2007 and 2016 update