Most important principle in recurrent surgery

Always have exposure more than the previous exposure.
Definitely have the bony margins exposed. If needed extend the craniotomy or laminotomy.
Definitely have normal dura exposed above and below the level of previous dural exposure. Without following these principles it is not possible to have safe surgery.
These principles hold good for both brain and spine surgery.

A big thanks for all my well wishers

Yes, It's official now.
After a very stressful period of 3 year Neurosurgical training I have cleared the final M.Ch examination.
All the credit goes to my boss who took pains to teach me good neurosurgical practice.
I also thank the Assistant Professors in the department for encouraging me all these days.
I should acknowledge my family for the support given in these 3 years.

MCA Segments

The middle cerebral artery can be classified into 4 parts:

M1Segment : Called as Sphenoidal Segment, due to its origin and loose lateral tracking of the sphenoid bone. It is also called as the Horizontal Segment. Starts at the point of carotid bifurcation and ends at Limen Insulae.

M2 segment : Extending anteriorly on the insula, this segment in known as the Insular Segment. It is also known as the Sylvian segment. The MCA branches may bifurcate or sometimes trifurcate into trunks in this segment .

M3 segment : This segment is also called Opercular Segment and extends laterally exteriorly from the insula towards the cortex.

M4 Segment : Called Cortical Segment. These begin at the external to the Sylvian fissure and extend distally away on the cortex of the brain.

Townes view

It is taken with the patient in the supine position and lying on his back with the chin often depressed into the neck. 

The X-ray camera is angled at 30 degrees towards the feet so that the rays enter the head at the level of the hair-line.

The result is clear image of the posterior portion of the skull including the foramen magnum.

A reversed Towne's view is obtained by taking the radiograph from the posterior with the patient lying face down.

The stuctures that are demonstrated in Town's view are

Details of occipital bone(1)

Lambdoid suture (2)

Outline of Foramen magnum (3)

Dorsum Sellae (4) (White shadow in the foramen magnum)

Occipital crest (5)

Some of the details of the temporal bone like petrous ridge are also identified (1)

Angiographic Shifts Seen With IC Masses

When cerebral angiography was the mainstay of diagnosis certain displacements of the vessels principally pericallosal vessels in the angiogram were used as indirect evidences for the location of the masses in various regions of the brain.

These shifts are

• Round shift = Frontal lesion anterior to coronal suture
• Square shift = Lesion behind foramen of Monro in lower half of hemisphere
• Distal shift = Posterior to coronal suture in upper half of hemisphere
• Proximal shift = Basifrontal lesion / anterior middle cranial fossa including anterior temporal lobe

Sylvian Point (Angiographic)

The angiographic sylvian point (ASP) is the most medial point where the last cortical MCA branch ( usually the angular artery) turns inferiorly to exit the sylvian fissure. 

This point approximates the apex of the insula and represents the posterior limit of the lateral cerebral sulcus. 

It is suggested to be the halfway point on the clinoparietal line (CPL) (CPL is the line between the anterior clinoid process and a pointon the skull roof situated 2 cm above the lambda or 8to9 cm obove the external occipital protrubarence).

It is seen in tha AP view.

Sylvian triangle (Angiographic)

Sylvian triangle =  A triangle formed by branches of MCA within sylvian fissure on outer surface of insula (form a loop) upon reaching the upper margin of the insula.

Anatomically it is demarcated by the superior insular line ( A line tangent to the tops of the insular loops), The main MCA trunk ( forms the posterior inferior margin of the triangle) and the most anterior branch of the ascending frontal complex ( forms the anterior border of the triangle) 

It is seen in lateral view and serves as angiographic landmark for localizing supratentorial masses. 

Schlesinger in 1953 identified and publicized this.

Radiation Necrosis

Necrosis of brain following radiation can be seen as an early delayed complication or late delayed complication.
The early delayed radiation necrosis may be seen with in 2 months of irradiation (Range 1 to 4 Months). This is a very rare entity. The pathological process might represent an autoimmune response following sensitization by a necrobiotic process induced by radiation.

The late delayed radiation necrosis commonly presents as a mass lesion.
The true incidence and natural history of late delayed radiation necrosis are not known. Most commonly late delayed radiation affects present at a mean duration of 14 months, but can occur as early as 6 months or as late as 5 years after completion of treatment.
The primary mechanism of the late delayed radiation necrosis is coagulative necrosis affecting the white matter secondary to small artery endothelial injury or direct damage to oligodendroglia.
Its incidence has been estimated as 5% in patients who have received greater than 45 Gy in fractions of 2 Gy per day.
25% of patients may suffer from radiation necrosis if the areas of the brain have received a total radiation dose of 60Gy or more.
4 facors critical in the occurance of radiation necrosis are
1. Total dose of radiation
2. Overall time of administration
3. Size of each fraction of Radiation
4. Number of fractions per irradiation

Epiconus, Conus and Cauda Equina syndromes

Epiconus Syndrome:

The epiconus syndrome presents with the following clinical features.

A sensory disturbance in the leg (transverse, saddle, radicular, or socks type).

Motor deficit as a sign of lower motor neuron involvement (foot drop, fasciculation, muscle atrophy).

Diminished deep tendon reflexes.

Occasional coexistence of positive pathological reflexes (Babinski's and Chaddock's signs).

Diminished vibration sensation, and

Bladder and bowel dysfunction.

Conus Medullaris Syndrome:

Mixed LMN and UMN type of picture seen

During the Acute phase paralysis of lower extremities with flaccid rectal tone and urinary retention are found.

In chronic phase there is evidence of atrophy and hyperreflexia.

The defecits tend to be symmetrical.

The prognosis for bowel and bladder function is relatively poor.

In pure Conus medullaris syndrome as in Intramedullary lesions there is total absence of motor disturbances inlower limbs and absent Babinski and other pathological pyramidal tract signs

CaudaEquina Syndrome:

Early radicular type of pain, Late sphincter disturbances,  and Asymmetrical sensory findings are characteristics.

Pain is unilateral or asymmetrical 

Develops flaccid, Hypotonic, areflexic paralysis true peripheral type of paraplegia.

Asymmetric sensory loss in saddle region involving anal, perineal and genital regions.

Ankle jerk is absent and has variable Knee jerk

Epiconus, Conus, Periconus and Cauda Equina

Anatomically, the epiconus comprises the cord segment between L4 and S1, corresponding to the T12 and L1 vertebrae.*

The conus medullaris consists of the cord segment between S2 and S5 as well as coccygeal segments.**

Anatomically periconus includes the Epiconus and Conus Medullaris

The cauda equina is a structure within the lower end of the spinal column that consists of nerve roots and rootlets from spinal segments L3 to Coccygeal nerve. At the base of the Cauda Equina, there are approximately 10 root pairs, 3-5 lumbar, 5 sacral, and the single coccygeal nerve.

*= Bullough P G, Boachie-Adjei O. Development of the Spinal Cord. 

 In: Atlas of the Spinal Diseases. JB Lippincott: Philadelphia, 1988,pp53.

** =  Di Pietro M A. The conusmedullaris : normal US findings throughout childhood.

Radiology 1993; 188: 149 - 153.

Multifocal Gliomas

Multi focal gliomas are categorised

1. Spatially as connected or disconnected

2. Temporally as Synchronous ( if present with initial presentation and Metachronous ( if develop during the follow up)

Multifocal glimas are called

1. Multiple - If they are present at the same time but are separated spatially 

2. Multicentric - If they are separated both spatially and temporally

Kindling

Kindling = easily combustible material for starting a fire (Webster's Dictionary) .

In Neurology

Def: The tendency of some regions of the brain to react to repeated low-level electrical stimulation by progressively boosting electrical discharges, thereby lowering seizure thresholds.

The phenomenon of kindling in epilepsy was first discovered accidentally by Graham Goddard in 1967 when studying the learning process in rats which included electrical stimulation of the rats' brains at a very low intensity, too low to cause any type of convulsion.

Goddard and others later demonstrated that it was possible to induce kindling chemically as well (Hargreaves, 1996.)

Kindling is a widely used model for the development of seizures and epilepsy in which the duration and behavioral involvement of induced seizures increases after seizures are induced repeatedly.

It is used by scientists to study the effects of repeated seizures on the brain.

In the kindling model, seizures begin to occur spontaneously after repeated subconvulsive stimul.

The seizure that occurs after the first electrical stimulation lasts a short time and is accompanied by a small amount of behavioral effects compared with seizures that result from repeated stimulations.

The lengthening of duration and intensification of behavioral accompaniment eventually reaches a plateau after repeated stimulation.

Criteria for Neurofibramatosis II

NF II Due to mutation of chromosome 22

Presence of one of the following

1. Bilateral eigth nerve masses seen with appropriate imaging technique

2. A parent, sibling or child with NF II and either a unilateral mass of either CN mass or any two of the following

Neurofibroma

Meningioma

Glioma

Schwannoma

Juvenile posterior subcapsular lenticular atrophy