If you're studying for the INBDE, I highly recommend INBDE Boot Camp, an all-in-one study resource that will help you pass your exam. Use coupon code MENTALDENTAL for 10% off. Hey everyone, Dr. Ryan here, and welcome back to our oral diagnosis series. Let's finish up this section.
by talking about developmental problems that directly involve the maxilla and the mandible, the jawbones themselves. So we're going to start with three terms that all end with the suffix nathia, which refers to the jaws. While these next three conditions can technically refer to either the maxilla or the mandible, they're more commonly used in reference to the mandible.
Macronathia is defined as an abnormally large jaw, again usually the mandible. It can happen in isolation or it can be associated with pituitary gigantism, tumors, and other disorders. Gigantism is also associated with macrodontia, big teeth, and macroglossia, big tongue.
The jaw discrepancy can be corrected with orthognathic surgery later in life. Micronathia is the opposite issue, defined as an abnormally small jaw, specifically referring to the mandible once again. It's often a symptom of a craniofacial condition like hemifacial microsomia or Treacher-Collins syndrome, both of which we'll briefly discuss later in this video.
Having a small mandible may interfere with daily functions like speaking, eating, and breathing. Just like anodontia means missing teeth, anathia means missing jaw. This a prefix usually indicates some negative like not or without. So anathia is an extremely rare congenital condition where the patient is entirely missing one or both jaws. It's caused by a disruption to the development of the first branchial arch.
It usually occurs as part of the anathia-odocephaly complex, which is unfortunately lethal, but an isolated incidence of anathia alone could have a better prognosis with acute airway management and careful treatment throughout life. Before we continue, I have to tell you about this incredible AI study tool that will help quiz you. on what you're learning in this video and it's called Wisdolia.
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Hemifacial microsomia, also called craniofacial, microsomia is a condition where half of the face is underdeveloped and doesn't grow normally. Hemifacial means hemisphere or half of the face, microsomia meaning smallness. This is the second most common facial birth defect by the way after cleft lip and cleft palate, affecting about one in every four thousand births. It's caused by an inadequate migration of neural crest cells to the first and second branchial arches on one side of the face.
And by the way, when I say branchial arches, a synonym to that would be pharyngeal arches. The affected side not only has a deficient mandible, but it also has deficient muscles of mastication, microtia, which means a small ear, and crossbite and crowding also on that affected side. Hemifacial hypertrophy is the opposite issue, where half of the face is overdeveloped. This usually includes early tooth eruption, open bite malocclusion, macrodontia, and macroglossia on the affected side.
Like macroglossia, it's also linked to Beckwith-Weidman syndrome. So I'm going to give you another helpful mnemonic. When you think of Beckwith-Weidman, think big and wide.
So big tongue and wide on one side of the face. By the way, hemifacial hypertrophy is related to, but not quite the same as hemihyperplasia or hemihypertrophy, which affects half of the entire body, limbs included. So hemifacial hypertrophy is a specific type of hemihyperplasia that affects only the face. Next up is Treacher-Collins syndrome.
This syndrome is caused by a genetic mutation inherited as an autosomal dominant trait that alters the development of neural crest cells causing a lack of facial bones and tissues. Like hemifacial microsomia, it involves an inadequate migration of neural crest cells to the first and second brachial arches, but this time on both sides of the face. Specifically, you end up with an underdeveloped mandible.
This condition is also called mandibulofacial dysostosis, which means a failure of the mandible bone to develop properly. Also, you can look at how this antigoneal notch is very deep. As far as the face, everything kind of droops down a little bit. The palpebral fissures, which are the openings of the eye between the eyelids, droop downwards as you can see in both of these images. ears are often small and malformed, once again called microtia, and these patients also have an increased chance of cleft palate, which occurs in about one-third of these syndromic patients.
As with Treacher-Collins syndrome, Epert syndrome is inherited via an autosomal dominant pattern. A main feature of this syndrome is premature closure of the bones of the skull called craniosynostosis. This early fusion prevents the skull from growing normally and affects the eventual shape of the head and the face. For example, you can appreciate the prominent forehead of this patient which is also called frontal bossing.
This process also affects brain development and is often accompanied by an intellectual disability. The eyes tend to be widely spaced from each other, which is called hypertelarism, and they can be bulging as well, which is called proptosis. The maxilla is often hypoplastic and undersized, and there's once again cleft palate in roughly one-third of these syndromic patients.
There also tends to be a narrow, high-vaulted palate called a Byzantine arch palate due to its similarity to that particular architectural structure. Children with Ebert syndrome also typically experience syndactyly, a condition in which their fingers and toes are webbed or conjoined together. Last we have Crouzon syndrome, also called craniofacial dysostosis, which is another autosomal dominant craniosynostosis syndrome.
In fact, it's the most common of all the craniofacial syndromes. It has a lot of similarities to Apert syndrome, except it's usually less severe and does not have any digital anomalies, so no webbed digits. There's also no intellectual disability.
Also note that patients with Crouzon syndrome are more likely to have a cleft lip and or cleft palate compared to the average person though it's not one of the most common features of the syndrome. Everything else listed here, the craniosynostosis, frontal bossing, underdeveloped maxilla, hypertelarism, and proptosis are main features of the syndrome. That's it for this video lecture. Thank you so much for watching.
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