Basic Science Neurosurgery

  1. How is the circle of Willis formed? What are its surgical importance? [TU 2060,63,66,68/6]
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  2. 1. List the cranial nerve nuclei in medulla oblongata and mention their functional components. 2054
  3. Describe the layers, blood supply, nerve supply and applied anatomy of the scalp. [TU 2067/2]
    Layers of scalp

    • S: skin
    • C: connective tissue
    • A: (galea) aponeurosis
    • L: loose connective tissue
    • P: periosteum [@ SCALP]
  4. Arterial supply of scalp?
    • The scalp has a rich blood supply and a small cut may cause profuse bleeding. The following arteries supply the scalp:
    • i. Supratrochlear and supraorbital arteries, branches of ophthalmic artery run along the corresponding nerves
    • ii. Superficial temporal artery, the smaller terminal branch of the external carotid artery runs up infront of the tragus along with auriculotemporal nerve.
    • iii. Posterior auricular artery, a branch of external carotid artery ascends pehind the pinna.
    • iv. occipital artery, a branch of external carotid artery runs up in occipteal region along with greater occipital nerve.

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  5. Venous drainage of scalp?
    • i. Supratrochlear and supraorbital veins, which joins at the medial angle of the orbit to form the facial vein
    • ii. Superficial temporal vein, which joins with the maxillary veins in the substance of the parotid gland to form the retromandibular vein.
    • ii. Posterior auricular vein, which joins with the posterior division of the retromandibular vein to form the external jugular vein.
    • iv. occipital vein, which drains into the occipitial venous plexus. The occipitial venous drains into both the vertebral vein or internal jugular vein.
  6. Nerve supply of scalp?
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  7. Describe the ventricular system of CNS. How is the CSF formed and how does it reach the subarachnoid space? [TU 2056]

    Short note on Ventricles of CNS and the formation and circulation of CSF. [TU 2055]
    Production - choroid plexus [@ Choroid Creates]

    Absorption – in arachnoid granulations that drain into venous sinuses. [@ Arachnoid Absorbs] The arachnoid villi responsible for absorption protrude mainly in superior sagittal sinus.

    Foramens for Communication of CSF

    • Foramen of Monro - Point of communication between the third and lateral ventricles. 
    • Foramen of Magendie - Connects the fourth ventricle to the subarachnoid space Medially.
    • Foramen of Luschka - Connects the fourth ventricle to the subarachnoid space Laterally
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  8. Functional component of the vagus nerve and their nuclei.
    Nuclei // Function

    Nucleus Solitarius // Visceral Sensory information (e.g., taste, baroreceptor, gut distention)

    Nucleus aMbiguus // Motor innervation of pharynx, larynx and upper esophagus (e.g., swallowing, palate elevation)

    Dorsal nucleus  of vagus // Parasympathetic function
  9. Intra-abdominal component of vagus nerve and its surgical importance. [TU 2060]
    Origin at Medulla, exits from Jugular foramen. 

    Descends vertically within the carotid sheath along with internal and common carotid arteries and internal jugular vein (IJV). 

    Neck branches - Superior laryngeal and recurrent laryngeal nerve. 

    Thoracic branches - Pulmonary plexus and cardiac plexus. 

    At lower end of esophagus - Esophageal plexus 

    The anterior and posterior gastric nerves are then formed from the esophageal plexus. The anterior gastric is formed mainly from the left vagus, but it does contain fibers from the right vagus.

    Similarly, the posterior gastric nerve is formed mainly from the right vagus but contains fibers from the left vagus nerve.

    The gastric nerves supply all abdominal organs and the gastrointestinal tract ending just before the left colonic (splenic) flexure (see the images below).

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  10. Nuclei of trigeminal nerve. [TU 2056]
    • The nucleus is divided into three parts, from rostral to caudal (top to bottom in humans):
    • The mesencephalic nucleus
    • The chief sensory nucleus (main sensory nucleus" or "primary nucleus" or "principal nucleus")
    • The spinal trigeminal nucleus
  11. Discuss the clinical importance of the danger area of the face 2067/2
    • It consists of the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla.
    • The facial vein is the largest vein of the face. It communicates with deep veins of the face through a communication between supraorbital and superior ophthalmic veins. 
    • These communications connect the facial vein with cavernous sinus.
    • These veins lack one-way valve. So, it is possible for retrograde infections from the nasal area to spread to the brain.
    • The most feared consequence of infection in danger area of face is cavernous sinus thrombosis.
  12. Mention the extent, course and clinical importance of middle meningeal artery. [TU 2061/5]
    The middle meningeal artery branches off the first part of the maxillary artery. It passes vertically through the roots of the auricotemporal nerve and enters the middle cranial fossa via the foramen spinosum. Here it gives off two branches - superior tympanic branch and ganglionic branch - before dividing into anterior and posterior divisions:

    • The anterior division runs anterolaterally through the middle cranial fossa on the greater wing of sphenoid before coursing superiorly, often grooving the bone, and passes under the pterion before giving its terminal branches over the upper parietal bone.
    • The posterior division runs horizontally posteriorly over the squamous part of the temporal bone to gives its terminal branches over the lower parietal bone.

    Clinical significance - It can be torn in head injuries resulting in extradural haemorrhage.
  13. 11. Briefly describe the steps involved in excitation-contraction of skeletal muscle
    • 13. Describe the intra-abdominal components of vagus nerve and their surgical importance. 8 2060/12
    • 14. Name different types of general sensation you can test clinically. Trace the pathway of general sensation from the area of angle of mandible. 3 2064/5
    • 15. Mention the nerve supply of tongue. How do you test these nerves clinically? 2068/5
    • 16. Mention nerve supply of tongue. How do you clinically test these nerves 2063/12
  14. Pathways of corticospinal tract and its clinical feature in lesions. 2057
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Basic Science Neurosurgery