Norma Basalis

Norma Basalis

“What is norma basalis? A detailed question and answers guide”

 Foramen magnum

• Foramen magnum is largest foramen of the skull
• Opens into posterior cranial fossa-upwards and into vertebral canal- downward
•  Foramen magnum is oval in shape
•  Foramen magnum is overlapped on each side by the occipital condyles

 Foramen magnum Structures Passing Through It:

• Anterior part-3 structures
  • Apical ligament of dens
  • Vertical band of cruciate ligament
  • Membrana tectoria
• Posterior part-2 structures
  • Lower part of medulla oblongata
  • 3 meninges
• Through subarachnoid space- 9 Structures
  • Spinal accessory nerves -2
  • Vertebral arteries – 2
  • Sympathetic plexus around the vertebral arteries -2
  • Posterior spinal arteries – 2
  • Anterior spinal artery – 1

“Understanding norma basalis through FAQs: Anatomy, structures, and uses explained”

Structures passing through foramen magnum

• Anterior part-3 structures
  • Apical ligament of dens
  • Vertical band of cruciate ligament
  • Membrana tectoria
• Posterior part-2 structures
  • Lower part of medulla oblongata
  • 3 meninges
• Through subarachnoid space-9 Structures
  • Spinal accessory nerves -2
  • Vertebral arteries – 2
  • Sympathetic plexus around the vertebral arteries -2
  • Posterior spinal arteries – 2
  • Anterior spinal artery – 1

“Importance of studying norma basalis for medical students: Questions explained”

 Foramen of middle cranial fossa

“Common challenges in mastering norma basalis notes effectively: FAQs provided”

Diploic veins

• The diploic veins are large, thin-walled valveless veins that channel in the diploë between the inner and outer layers of the cortical bone in the skull.
• They develop fully by the age of two years.
• The diploic veins drain this area into the dural venous sinuses.
• The four major types of diploic veins found on each side of the head are frontal, anterior temporal, posterior temporal, and occipital diploic veins.

Types:

Auditory tube

• The auditory tube connects the middle ear with the nasopharynx anteriorly
• The sulcus tube which is a groove between the posteromedial margin of the greater wing of the sphenoid & the petrous temporal bone lodges the cartilaginous part of the auditory tube

Pterygomaxillary fissure

• Pterygomaxillary fissure is a triangular interval formed by the divergence of the maxilla from the pterygoid process of the sphenoid
• Pterygomaxillary fissure connects infratemporal with the Pterygopalatine fossa
• Pterygomaxillary fissure transmits terminal part of internal maxillary artery

“Why is identifying norma basalis critical for skull base surgery? Answered”

Pterygopalatine Fossa

Pterygopalatine Fossa Location:

• Lies deep to the pterygomaxillary fissure

Pterygopalatine Fossa Boundaries:

1. Anterior
   • Posterior surface of maxilla
2. Posterior
   • Pterygoid process
   • Greater wing of sphenoid
3. Medial
   • Perpendicular place of palatine bone
4. Floor
   • Union of anterior & posterior walls

Pterygopalatine Fossa Contents:

• Maxillary nerve & its branches
• 3rd part of maxillary artery & its branches
• Pterygopalatine ganglion with its branches

“Factors influencing success with norma basalis studies: Q&A”

Contents Of Pterygopalatine Fossa

3 contents:

• Maxillary nerve & its branches
• 3rd part of maxillary artery & its branches
• Pterygopalatine ganglion with its branches

3 ganglion:

• Sphenopalatine
• Pterygopalatine
• Ganglion of hay fever

3 structures transversing in posterior wall:

• Maxillary nerve
• Nerve of pterygoid canal
• Pharyngeal branch through pterygoid canal

3 structures passing through inferior orbital fissure

• Infraorbital nerve
• Zygomatic nerve
• Orbital branches of the ganglion

3 structures through inferior opening:

• Anterior palatine nerve & greater palatine vessels
• 2 Posterior palatine nerve & lesser palatine vessels

3 structures through medial opening:

• Nasopalatine nerve & sphenopalatine vessels
• Medial posterosuperior nasal branches
• Lateral posterosuperior nasal branches

3 roots of the ganglion:

• Sensory
• Sympathetic
• Secretomotor

“Steps to explain clinical relevance of norma basalis: Surgical planning vs trauma management vs imaging techniques: Q&A guide”

Pterygopalatine ganglion

• Pterygopalatine ganglion is largest parasympathetic ganglion

Pterygopalatine ganglion Roots

Pterygopalatine ganglion Branches

“Role of norma basalis in guiding surgical approaches: Questions answered”

• Posteriorly, the groove leads to the bony part of the auditory tube, which lies within the petrous temporal bone

Pterygopalatine ganglion Parts

1. Osseous part-36 mm long
2. Fibro-cartilaginous part-24 mm long

Pterygopalatine ganglion Arterial Supply:

• Middle meningeal artery
• Artery of the pterygoid canal
• Ascending pharyngeal branch of external carotid artery

Pterygopalatine ganglion Venous Drainage:

• Pterygoid & pharyngeal Venous plexus

Pterygopalatine ganglion Function:

• Maintains equilibrium of air pressure

Foramen magnum

• Foramen magnum is largest foramen of the skull
• Opens into posterior cranial fossa-upwards and into vertebral canal- downward
• Foramen magnum is oval in shape
• Foramen magnum is overlapped on each side by the occipital condyles

“How does trauma to norma basalis affect cranial nerves? FAQ explained”

 Jugular foramen

•  Jugular foramen is large & elongated.
•  Jugular foramen is placed at the posterior end of the petro-occipital suture

 Jugular foramen Structures passing through it:

• Anterior part:
  • Inferior petrosal sinus
  • Meningeal branch of ascending pharyngeal artery
• Middle part:
  • Glossopharyngeal nerve
  • Vagus nerve
  • Accessory nerve
• Posterior part:
  • Internal jugular vein
  • Meningeal branch of occipital artery

“Early warning signs of poor adherence to skull base principles: Common questions”

Foramen lacerum

• Foramen lacerum is short, wide canal, 1 cm long
  • Bounded by
• Posterolaterally: by apex of the petrous temporal bone
• Medially:
  • Basiocciput
  • Body of the sphenoid
• Anteriorly
  • Root of the pterygoid process
  • Greater wing of the sphenoid bone

Foramen lacerum Structures passing through it:

• Lower part
  • Meningeal branch of ascending pharyngeal artery
  • Emissary vein
• Upper part
  • Internal carotid artery
  • Venous & sympathetic plexuses around it
• Anterior part
  • Nerve of the pterygoid canal

Superior orbital fissure

• Superior orbital fissure is situated at the posterior part of the junction between the roof & lateral wall of the orbit
• Superior orbital fissure is an oblique, roughly triangular space bounded
  • Above by the lesser wing
  • Below by the greater wing
  • Medially by the body of the sphenoid

Structures passing through it:

• Lateral part:
  • Nerves: lacrimal, frontal, trochlear
  • Vein: superior ophthalmic
  • Arteries: meningeal branch of lacrimal artery, anastomotic branch of middle meningeal artery
• Middle part:
  • Upper & lower division of oculumotor nerve
  • Nasociliary nerve
  • Abducent nerve
• Medial part:
  • Inferior ophthalmic vein
  • Sympathetic nerves from the plexus around internal carotid artery

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Structures passing through foramen ovale

Male:

• Mandibular nerve
• Accessory meningeal artery
• Lesser petrosal nerve
• Emissary vein

Structures passing through foramen spinosum

Structures passing through foramen spinosum are:

• Middle meningeal artery
• Meningeal branch of mandibular nerve
• Posterior trunk of middle meningeal vein

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 Structures passing through superior orbital fissure

• Lateral part
  • Nerves: lacrimal, frontal, trochlear
  • Veins: superior ophthalmic
  • Arteries: meningeal branch of lacrimal artery, anastomotic branch of middle meningeal artery
• Middle part
  • Upper and lower division of oculomotor nerve
  • Nasociliary nerve
  • Abducent nerve
• Medial part
  • Inferior ophthalmic vein
  • Sympathetic nerves from the plexus around internal carotid artery

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Structures passing through anterior condylar canal

• Hypoglossal nerve
• Meningeal branch of the hypoglossal nerve
• Meningeal branch of ascending pharyngeal artery
• Emissary vein

 Foramen ovale

• Foramen ovale is large and oval in shape

Foramen ovale Location:

Posterolateral to the upper end of the posterior border of lateral pterygoid plate

Foramen ovale Structures passing through it:

Male:

• Mandibular nerve
• Accessory meningeal artery
• Lesser petrosal nerve
• Emissary vein

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