Foramen tympanicum
The foramen tympanicum (plural: foramina tympanica), also known as foramen of Huschke, is an anatomical variation in the external acoustic canal (EAC), where a bony defect connects the EAC to the temporomandibular joint (TMJ).
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Epidemiology
Various studies have reported on the occurrence of a foramen tympanicum in the asymptomatic population, with a reported prevalence of 4.6-20% 1-3.
Clinical presentation
Most cases are asymptomatic, but a patent foramen tympanicum has been reported as being the cause of persistent ear discharge following mastication due to the connection with the TMJ or fistula with the parotid gland 1,4,5. During TMJ arthroscopy, the foramen tympanicum may lead to inadvertent passage of the endoscope into the TMJ, with resulting damage 6-7. Spread of infection between the EAC and infratemporal fossa can also occur through this anatomical variation 1.
Gross anatomy
Development
The external ear canal is incompletely formed at birth, and further post-natal development results in two prominences (anterior and posterior) growing towards each other to form the EAC inferiorly. Lack of fusion of the anterior and posterior prominences with each other results in a persistent gap, the foramen tympanicum 6. Of note, the foramen tympanicum can close at up to 5 years of age, and hence it should only be diagnosed after this age 1.
Radiographic features
CT
High resolution CT of the petrous temporal bone is the imaging study of choice. The foramen tympanicum arises in the antero-inferior part of the EAC, and is postero-medial to the TMJ. The opposite side should be examined with care, as bilateral cases have been reported in 6% 2.
Treatment and prognosis
The foramen tympanicum is an incidental finding in most cases and does not need treatment in these cases. However, its presence should be sought if a patient presents with persistent ear discharge. Surgical treatment to obliterate the space between the EAC and TMJ is usually successful 8, and any other unusual specific pathology can be addressed at the time, e.g. parotid duct fistula, or herniation of TMJ synovium 9.
Differential diagnosis
External auditory cholesteatoma has to be excluded.
History and etymology
It was first described by Emil Huschke (1797-1858): German anatomist and embryologist.
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Anatomy: Head and neck
- skeleton of the head and neck
-
cranial vault
- scalp (mnemonic)
- fontanelle
-
sutures
- calvarial
- facial
- frontozygomatic suture
- frontomaxillary suture
- frontolacrimal suture
- frontonasal suture
- temporozygomatic suture
- zygomaticomaxillary suture
- parietotemporal suture (parietomastoid suture)
- occipitotemporal suture (occipitomastoid suture)
- sphenofrontal suture
- sphenozygomatic suture
- spheno-occipital suture (not a true suture)
- lacrimomaxillary suture
- nasomaxillary suture
- internasal suture
- basal/internal
- skull landmarks
- frontal bone
- temporal bone
- parietal bone
- occipital bone
- skull base (foramina)
-
facial bones
- midline single bones
- paired bilateral bones
- cervical spine
- hyoid bone
- laryngeal cartilages
-
cranial vault
- muscles of the head and neck
- muscles of the tongue (mnemonic)
- muscles of mastication
-
muscles of facial expression
- occipitalis muscle
- circumorbital and palpebral muscles
- nasal muscles
- buccolabial muscles
- elevators, retractors and evertors of the upper lip
- levator labii superioris alaeque nasalis muscle
- levator labii superioris muscle
- zygomaticus major muscle
- zygomaticus minor muscle
- malaris muscle
- levator anguli oris muscle
- risorius muscle
- depressors, retractors and evertors of the lower lip
- depressor labii inferioris muscle
- depressor anguli oris muscle
- mentalis muscle
- compound sphincter
- orbicularis oris muscle
- incisivus superior muscle
- incisivus inferior muscle
- muscle of mastication:
- elevators, retractors and evertors of the upper lip
- muscles of the middle ear
- orbital muscles
- muscles of the soft palate
- pharyngeal muscles
- suprahyoid muscles
- infrahyoid muscles
- intrinsic muscles of the larynx
- muscles of the neck
- accessory muscles of the neck
- deep cervical fascia
-
deep spaces of the neck
- anterior cervical space
- buccal space
- carotid space
- danger space
- deep cervical fascia
- infratemporal fossa
- masticator space
- parapharyngeal space
- stylomandibular tunnel
- parotid space
- pharyngeal (superficial) mucosal space
- perivertebral space
- posterior cervical space
- pterygopalatine fossa
- retropharyngeal space
- suprasternal space (of Burns)
- visceral space
- surgical triangles of the neck
- orbit
- ear
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common carotid artery
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common carotid artery
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arterial supply
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cranial nerves
- olfactory nerve (CN I)
- optic nerve (CN II)
- oculomotor nerve (CN III)
- trochlear nerve (CN IV)
-
trigeminal nerve (CN V) (mnemonic)
- trigeminal ganglion
- ophthalmic division
- maxillary division
- mandibular division
- abducens nerve (CN VI)
- facial nerve (CN VII)
-
vestibulocochlear nerve (CN VIII)
- vestibular ganglion (Scarpa's ganglion)
- glossopharyngeal nerve (CN IX)
-
vagus nerve (CN X)
- superior laryngeal nerve
- recurrent laryngeal nerve (inferior laryngeal nerve)
- (spinal) accessory nerve (CN XI)
- hypoglossal nerve (CN XII)
- parasympathetic ganglia of the head and neck
- greater occipital nerve
- third occipital nerve
-
cervical plexus
- muscular branches
- longus capitis
- longus colli
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ansa cervicalis
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- sternothyroid
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- phrenic nerve
- contribution to the accessory nerve (CN XI)
- cutaneous branches
- muscular branches
- brachial plexus
- pharyngeal plexus
-
cranial nerves
- lymphatic drainage of the head and neck
- embryological development of the head and neck
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