Describe the clinical anatomy of Prussak’s. Enumerate its clinical significance in chronic otitis media.
Prussak’s Space is the small middle ear recess and is the sub-component of lateral epitympanic space.
It is named after the Russian otologist Alexander Prussak (1839-1897) .
The Prussak’s space is formed from the posterior pouch of von Troltsch as a prolongation of either a lower portion or a higher portion of the superior saccus, replacing the mesenchymal tissue between the neck of the malleus and Sharpnell,s memberane. It communicates with the posterior pouch of von Troltsch.
The Prussak,s space is situated inferior to the tympanic diaphragm and represents the lower unit of the attic.
Laterally, it extends superior to the roof of EAC by 0.4 mm and attains its largest cross section of 2.6 mm at the level of roof of EAC.
Medially: neck of malleus and lateral malleolar ligament.
Laterally: pars falccida
Inferiorly: lateral process of malleus
Superiorly: lateral malleolar fold and scutum
Anteriorly: Anterior malleolar ligament
From the neck of malleus the anterior, malleolar fold and the anterior ligament arise, demarcating Prussak’s space anteriorly. Ventilation of Prussak’s space is only possible posteriorly above the posterior malleus.
Prussak’s space is important because it is site for acquired cholesteatoma formation. It is the potential space which may first be involved during extension of cholesteatoma. This space can play an important role in the retenttion of keratin and subsequent development of cholesteatom. A cholesteatom forms when there is a deep retraction pocket in the tympanic membrane. The lining of the tympanic membrane, which is skin (epithelium), is shed,but if the membrane is retracted it gets trapped. The debris collects and enlarges and ultimately form a cholesteatoma. This cholesteatoma, in turn, can erode the middle ear ossicles, facial nerve, inner ear and even involve the brain.
Prussak’s Space Dysventilation and Attical Cholesteatoma:
The possibility of closure of posterior pouch of von Troltsch following thick mucus secretion formation during chronic inflammatory otitis is high.
This cause a selective dysventilation of Prussak’s space and development of pars flaccid retraction pocket with adhesion to the malleus neck.
This event may take place without any involvement of the other compartments of the upper unit that are situated superior to the tympanic diagram.
Initially the sac of retraction pocket remains small and superficial to the ossicles.
However, continued retraction and keratin accumulation lead to enlargement of sac and its expansion via pathways of least resistance.
From Prussak’s space, located in the epitympanum, cholesteatoma patterns of spread are:
Posterior epitympanum- through superior incudal space to mastoid antrum.
Posterior mesotympanum- inferiorly through the posterior pouch of von Troeltsch to the stapes, round window, sinus tympani and facial recess.
Anterior epitympanum- anterior to head of malleus, may gain access to supratubal recess via anterior pouch of von Troeltsch.