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

Diagnostic criteria for Neurofibramatosis I

NF I ( Mutation of chromosome 17)

Presence of 2 or more of the following

1. Six or more Cafe-au-Lait Spots of

           >5mm in pre pubertal age group 

           >15 mm in post pubertal age group

2. Two or more neurofibromas of any type or 1 plexiform neurofibroma

3. Freckling in axillary or Inguinal regions

4. Optic gliomas

5. Two or more Lisch nodules ( Slit lamp examination)

6. A distinctive ossesous lesion like Sphenoid dysplasia, Thinning of long bone cortex with or without pseudoarthrosis

7. A parent or sibling or child with NFI according to above criteria

Neurocutaneous markers

Various Neurocutaneous markers that can be seen are

1. Cafe-au-lait spots

2. Lisch Nodules ( Slit lamp Examination)

3. Axillary and inguinal freckling

4. Cutaneous Neurofibramatosis

5. Facial Angiofibromas

6. Multiple Ungual Fibromas

7. Shagreen Patch

8. Adenoma Sebaceum

9. Hyper / Hypo melanotic macules

10. "Confetti" Skin Lesions ( Brightly colored lesions)

11. Randomly distributed enamil pits in deciduous or permanent teeth

12. Gingival fibromas

13. Ash - Leaf Spots

14. Facial angioma or portwine stain 

15. Hemangiomas over the spine

16. Dermal sinus

17. Hairy tuft over sacrum

18. Sacral dimples and pits

Brachial Plexus Anatomy 2

Branches from the Roots (3 Branches)

1. Nerve to Serratus anterior - ( Long Thorasic nerve) - C5,6,7

2. Nerve to Subclavius - C5,C6

3. Dorsal scapular nerve - C4,C5

Branches from Trunks (1 Branch)

1. Suprascapular Nerve ( C5-C6) Supply Supraspinatus and Infraspinatus

There are no branches from Divisions

Branches from Cords

Medial cord ( 5 branches) - M4U

1. Medial pectoral nerve

2. Medial root of Median Nerve

3. Medial cutaneius nerve of arm

4. Medial Cutaneous nerve of fore arm

Lateral cord ( 3 branches) LML

1. Lateral root of Median Nerve

2. Musculocutaneous Nerve

2. Lateral pectoral Nerve

Posterior Cord (5 Branches) - ULNAR

1. Upper subscapular

2.Lower subscapular

3. Nerve to Lattismus dorsi ( Toracodorsal Nerve)

4. Axillary Nerve

5. Radial Neve

Brachial Plexus Anatomy

Formed from C5 to T1 Roots

Roots unite to form Trunks Upper , Middle and Lower trunks ( From the anterior border of Scalene anterior)

Three trunks divide into 3 anterior and 3 posterior divisions ( From the lateral border of 1st Rib)

anterior divisions of the upper, middle, and lower trunks
posterior divisions of the upper, middle, and lower trunks

In relation with the 1st part of Axillary artery form 3 Cords The Medial, Lateral and Posterior Cords

Branches emerge from the Cords

UMN Facial plasy

The UMN Facial pasly is the supranuclear palsy, charectaristically involves only the ipsilateral lower half of the face ( Upper half has bilateral supply)

It is of two types.

1. Mimetic Facial Palsy: Also called emotional facial paresis, characterized by clinically identifiable  facial palsy on mimetic movements like smiling, weeping e.t.c. There is no facial paresis with voluntary facial expression like showing teeth and closing eyes.

This is seen with lesions involving the contralateral frontal lobe anterior to the precentral gyrus, SMA, frontal lobe white matter, Mesial temporal lobe, insula, thalamus and subthalamus and post encephalitic parkinsonism.

2. Volitional Facial Palsy: The facial palsy is most marked on voluntary contraction of muscles and less so on mimetic movements.

This is seen with lesions interrupting the ipsilateral corticobulbar  fibers from the lower precentral gyrus, internalcapsule, cerebral peduncle, upper pons ( above facial nucleus)

Taylor-Haughton lines

In 1900 Taylor and Haughton described a technique to define a line on the scalp directly above the central (rolandic) fissure.

1. Draw a Nasion-Inoin line ( Nasion - Just below Glabella and Inion -External Occipital protruberanc)

2. Divide the Nasion-Inoin line in to 25%, 50% and 75%

3. Bregma is the point between the 25% and 50% points and Lambda is at 75% point

4. Sylvian fissure is drawn from the orbitotemporal angle (A point of depressin where eyebrow ends) to the 75% point on naso-inion line.

5. Draw a line perpendicular to the root of the zygoma starting at preauricular point 

6. Central sulcus is drawn from 54% point on naso-inoin line to the point where the sylvian line cuts the perpendicular line

Nucleus of Darkschewitsch and Cajal

Nucleus of Darkschewitsch: An ovoid cell group in the ventral central gray substance rostral to the oculomotor nucleus, receiving fibres from the vestibular nuclei by way of the medial longitudinal fasciculus; projections are not known, although some cross in the posterior commissure.

Nucleus of Cajal : A group of widely spaced, medium-sized neurones in the dorsomedial region of the upper mesencephalic tegmentum, immediately lateral to the nucleus of Darkschewitsch; together with the latter, the interstitial nucleus is closely associated with the medial longitudinal fasciculus, via which it receives fibres from the vestibular nuclei and projects crossed fibres via the posterior commissure to the oculomotor nucleus; also projects fibres to all spinal levels.

It is believed to be involved in the integration of head and eye movements, particularly eye movements of a vertical or oblique nature.

Structues passing in superior and inferior orbital fissures

Structures passing through Superior Orbital fissure

It is divided into 3 parts from lateral to medial

Lateral Part transmits: lacrimal nerve, frontal nerve, trochlear nerve, meningeal branch of lacrimal artery, anastomotic branch of middle meningeal artery which anastomoses with recurrent branch of the lacrimal artery

Middle Part transmits: Upper and lower divisions of the oculomotor nerve, nasociliary nerve between the two divisions of oculomotor nerve and abducent nerve

Medial Part transmits: Superior ophthalmic vein and sympathetic nerves from the plexus around internal carotid artery

Mnemonic for nerves in superior orbital fissure

Little FairyTold Sheena About New Ingrediants.

Lacrimal, Frontal, Trochlear, Superior Division of Oculomotor, Abducens, Nasociliary and Inferior Division of Oculomotor nerve.

Structures passing through Inferior Orbital fissure

It transmits the maxillary nerve and its zygomatic branch, and the ascending branches from the pterygopalatine ganglion.

The infraorbital vessels are not found in the inferior orbital fissure, but rather in the infraorbital foramen.

Short ciliary nerves

Branches of the ciliary ganglion.

6 to 10 in number, Arranged in 2 bundles at the superior and inferior angles of ciliary ganglion, Inferior bundle is large

Run forward with ciliary arteries ine above and one below the optic nerve.

Accompanied by long ciliary nerves.

They pierce the sclera at the back part of the bulb of the eye, pass forward in delicate grooves on the inner surface of the sclera, and are distributed to the Ciliaris muscle, iris, and cornea.

Contain both sympathetic and parasympathetic fibers.

Aqueduct of Sylvius

It is the cavity of diencephalon.

Also called the Mesencephalic duct or Cerebral Aqueduct.

It connects 3rd  ventricle to the 4th Ventricle.

The normal mean cross sectional area of the Aqueduct at birth is o.5 mm with a range from 0.2 to 1.8 mm.

In Aqueductal stenosis the size of the aqueduct is focally reduced either at the level of the superior colliculus or at the level of inferior colliculus.

In CT the Aqueduct is usually not visualized and this is attributed for the "Partial volume effect"

 

Nerve Fiber type and function

Erlanger and Gasser divided mammalian nerve fibers into A, B, and C groups.

 

Spurling's Maneuver

This is also called the foraminal compression test.

This test done in upper limbs is considered equivalent to SLR in lower limbs.

This is done to test cervical nerve root irritability in neck.

Standing behind the patient, head is bent backwards and flexed laterally to the symptomatic side.

This posture may elicit pain or paresthesia in the involved root.

If pain or paresthesia are not seen then a downward compression over the vertex is given to aggravate the foraminal compression so as to elicit the pain and paresthesia 

Hypoglossal Canal

Hypoglossal canal is the Bony canal which transmits the Hypoglossal nerve.

It is also called anterior condyloid foramen.

It is present in the Occipital Bone.

It lies in the epiphyseal junction between the basiocciput and the jugular process of the occipital bone.

This location corresponds to 10'O clock position on the left and 2'O clock position  in relation to the Foramen magnum.

The canal is superiorly surrounded by Jugular tubercle, Superio laterally by the Jugular foramen, laterally by the sigmoid sinus and inferiorly by the occipital condyle.