Attic area boundaries

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Here is a complete breakdown of the Attic (Epitympanum) - Area and Boundaries, drawn directly from KJ Lee's Essential Otolaryngology:

Attic (Epitympanum) - Definition

The attic is the upper portion of the middle ear cavity located above the level of the tympanic membrane and above an imaginary plane drawn through the short process of the malleus. It communicates with the mastoid antrum posteriorly and plays a fundamental role in middle ear ventilation routes.

Middle ear anatomy schematic showing the attic region in context with the Eustachian tube, facial nerve, mastoid antrum, and surrounding structures

Boundaries (Limits) of the Attic

Wall	Boundary
Superior	Tegmen tympani (thin bony plate separating it from the middle cranial fossa)
Inferior	Tympanic diaphragm and isthmus
Medial	Facial nerve canal and lateral semicircular canal
Lateral	Pars flaccida of the tympanic membrane + scutum (Chaussé spur)
Anterior	Zygomatic root
Posterior	Incudal fossa and aditus ad antrum

Internal Subdivision: Anterior vs. Posterior Epitympanum

The attic is divided by the superior malleal fold into two compartments:

Posterior epitympanum (posterior to superior malleal fold):

Posterior part of malleus head
Incus body and short process
Contains the posterior ventilation route - the most important pathway to the attic

Anterior epitympanum (anterior to superior malleal fold):

Anterior portion of malleus head
Contains the anterior ventilation route - an accessory pathway

Tympanic Diaphragm (inferior boundary)

The tympanic diaphragm (the floor of the attic) is composed of:

Posterior incudal ligament
Lateral incudomalleal fold
Lateral malleal fold
Lateral malleal ligament
Anterior malleal fold
Anterior malleal ligament
Tensor tympani fold (posterior malleal fold)
Tensor tympani muscle tendon

Tympanic Isthmus

A 2.5-mm opening in the tympanic diaphragm that ventilates the entire attic:

Anterior tympanic isthmus: between the incudostapedial joint and tensor tympani muscle tendon - the largest and most important ventilation route. Blockage here causes attic selective dysventilation, chronic edema, retraction pockets, and cholesteatoma.
Posterior tympanic isthmus: posterior to the incudostapedial joint, between the stapedial muscle tendon, pyramidal eminence, and incus short process.

Prussak Space (a key sub-space within the attic lateral wall)

Wall	Boundary
Superior	Lateral malleal fold (tympanic diaphragm)
Inferior	Malleus neck
Medial	Malleus head

Prussak space is clinically important as the most common site of origin for pars flaccida cholesteatoma.

KJ Lee's Essential Otolaryngology, p. 496-499

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