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Submandibular space

The submandibular space is a paired fascial compartment in the suprahyoid region of the head and neck, situated inferior to the mylohyoid muscle and superior to the hyoid bone, primarily containing the superficial portion of the submandibular salivary gland along with associated neurovascular structures and lymph nodes.^[1] This space forms part of the submandibular triangle, a topographic region bounded anteriorly by the anterior belly of the digastric muscle, posteriorly by the posterior belly of the digastric muscle, and superiorly by the inferior border of the mandible.^[2] The submandibular space is delimited laterally and anteriorly by the mandible, medially by the anterior belly of the digastric muscles, superiorly by the mylohyoid muscle, and inferiorly by the superficial layer of the deep cervical fascia overlying the hyoid bone.^[1] Its contents include the superficial lobe of the submandibular gland, submandibular lymph nodes (typically 3–6 in number, draining the lower gums, floor of the mouth, tongue, and tonsils), the facial artery and vein, portions of the hypoglossal nerve (cranial nerve XII), the lingual nerve (from the mandibular division of the trigeminal nerve), and the mylohyoid nerve.^[2] The space communicates posteriorly with adjacent compartments such as the sublingual and submental spaces, allowing potential spread of pathology across these boundaries.^[3] Clinically, the submandibular space is significant due to its susceptibility to infections, particularly odontogenic origins from mandibular molars, where pus tracks inferiorly below the mylohyoid muscle attachment, leading to cellulitis or abscess formation with symptoms including facial swelling, trismus, fever, and odynophagia.^[3] Severe infections can progress to Ludwig's angina, a bilateral cellulitis involving the submandibular, sublingual, and submental spaces that poses an airway emergency through edema and potential mediastinal extension.^[3] Other pathologies include sialadenitis (often from sialolithiasis obstructing the submandibular duct), benign and malignant neoplasms of the gland (such as pleomorphic adenoma or adenoid cystic carcinoma), and iatrogenic complications during surgical procedures like neck dissections, where injury to the marginal mandibular branch of the facial nerve may cause lower lip weakness.^[2] Imaging modalities like computed tomography (CT) are essential for evaluating extent, guiding drainage (often transoral), and monitoring treatment with broad-spectrum antibiotics.^[1]

Anatomy

Location

The submandibular space is a paired potential space located in the suprahyoid region of the neck.^[4] It corresponds to the submandibular triangle, which forms a division of the larger anterior triangle of the neck.^[2] Known in Latin as spatium submandibulare, this space is situated beneath the mandible and contributes to the structural framework of the floor of the mouth region.^[5] This space is positioned superficially and inferior to the mylohyoid muscle, which serves as its superior aspect without forming a complete enclosure.^[6] It lies between the anterior and posterior bellies of the digastric muscle, establishing its lateral and medial orientation within the suprahyoid neck.^[2] The submandibular space's proximity to the mandible underscores its role in the superficial compartment of the head and neck, adjacent to the oral cavity's inferior boundary.^[4]

Boundaries

The submandibular space is a paired potential space located in the suprahyoid region of the neck, enclosed primarily by the superficial layer of the deep cervical fascia that invests the mandible and hyoid bone.^[7] This fascial envelope forms a structural compartment that separates the space from surrounding tissues, with the space existing bilaterally but capable of midline communication through the submental region.^[2] Anteriorly and laterally, the submandibular space is bounded by the medial surface of the mandible, which provides a bony limit extending from the symphysis to the angle of the jaw.^[7] Medially, it is delimited by the anterior belly of the digastric muscle, which originates from the digastric fossa near the midline and courses superiorly and laterally toward the mandible.^[2] Superiorly, the inferior surface of the mylohyoid muscle serves as the roof, spanning from the mylohyoid line of the mandible to the hyoid bone and separating the space from the oral cavity floor.^[7] Posteriorly, the boundary is formed by the posterior belly of the digastric muscle and the stylohyoid muscle, with the former arising from the mastoid notch and the latter extending from the styloid process to the hyoid, together creating a muscular posterior limit near the angle of the mandible.^[8] Inferiorly, the space is confined by the hyoid bone superior to the attachment of the superficial layer of the deep cervical fascia, which continues downward to blend with deeper fascial planes.^[2] This arrangement establishes the submandibular space as a distinct bilateral compartment, though its medial aspects allow potential continuity across the midline via adjacent fascial planes.^[7]

The submandibular space primarily contains the submandibular salivary gland, which is divided into superficial and deep lobes that wrap around the mylohyoid muscle, enclosed laterally by the anterior and posterior bellies of the digastric muscle.^[2] The superficial lobe occupies most of the space anteriorly and laterally, appearing almond-shaped and running parallel to the anterior digastric muscle, while the deep lobe is smaller and triangular, located superomedially to the mylohyoid muscle and containing the glandular hilum from which the submandibular duct (Wharton's duct) emerges.^[9] This gland, the second largest major salivary gland, produces a viscous, mucinous saliva that contributes significantly to oral lubrication and digestion.^[2] Vascular structures within the space include the facial artery and vein, which provide arterial supply and venous drainage to the region. The facial artery, a branch of the external carotid artery, loops anteriorly around the mandible and passes deep to the posterior aspect of the submandibular gland before crossing the mandible inferiorly.^[2] The accompanying facial vein runs more superficially along the lateral aspect of the gland, eventually joining the retromandibular vein to form the common facial vein, which drains into the internal jugular vein.^[2] These vessels support the neurovascular supply to the floor of the mouth and adjacent oral structures.^[1] Neural components consist of the hypoglossal nerve (cranial nerve XII) and branches of the lingual nerve. The hypoglossal nerve courses through the deep portion of the space, providing motor innervation to the intrinsic and extrinsic muscles of the tongue.^[1] The lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3), traverses the space deeper to the submandibular gland, carrying sensory fibers to the anterior two-thirds of the tongue and floor of the mouth; it also gives off branches that connect to the submandibular ganglion for parasympathetic innervation.^[2] Lymphatic structures include the submandibular lymph nodes, typically numbering 3 to 6, which are situated adjacent to the submandibular gland in levels Ib (submandibular) and II (upper jugular) of the neck. These nodes drain the inferior portions of the oral cavity, including the lower gums, tongue, floor of the mouth, and tonsils, playing a key role in regional lymphatic drainage.^[2] Additionally, minor salivary tissues may be present as small accessory glandular elements within the fatty connective tissue of the space, contributing modestly to local saliva production alongside the dominant major gland.^[1] Collectively, these contents facilitate essential functions: the submandibular gland drives saliva production for oral health, the lymph nodes ensure lymphatic drainage from oral and facial structures, and the neurovascular elements supply sensory, motor, and blood flow needs to the floor of the mouth.^[2]

Communications

The submandibular space, a paired potential space in the suprahyoid neck, communicates with several adjacent fascial compartments, facilitating the potential spread of fluid, infection, or pathology through loose connective tissue and permeable fascial planes. These interconnections are primarily defined by muscular and fascial boundaries that lack complete septation, allowing diffusion across the anterior digastric bellies, posterior mylohyoid edges, and inferior extensions.^[1]^[10] Anteriorly and medially, the submandibular spaces communicate with the midline submental space across the anterior bellies of the digastric muscles, where the intervening fat-filled region permits continuity between the paired submandibular compartments without rigid fascial division. This pathway is bounded by the mylohyoid muscle inferiorly and the mandible superiorly, enabling free passage of contents in the submental triangle.^[10] Superiorly, communication with the sublingual space is limited but occurs primarily through defects in the mylohyoid muscle, including the posterior free edge where a gap exists between the mylohyoid and hyoglossus muscles, as well as midportion boutonniere defects present in 35–50% of individuals that allow herniation of sublingual gland or fat. Additional limited access is provided along neurovascular bundles traversing these muscular sling defects.^[11]^[1] Posteriorly and inferiorly, the submandibular space connects with the lateral pharyngeal (prestyloid parapharyngeal) space behind the posterior belly of the digastric muscle, through the buccopharyngeal gap along the styloglossus muscle and via open fascial continuity at the hyoid level. This interconnection is enhanced by the absence of separating fascia in the inferior parapharyngeal space, promoting diffusion posterior to the digastric.^[1]^[12] The loose areolar connective tissue filling these spaces, combined with the superficial layer of the deep cervical fascia, plays a critical role in permitting free diffusion across these boundaries, as the fascial planes are thin and non-barrier-forming in these regions. Inferiorly, there are no rigid barriers toward the carotid triangle, with the space opening openly between the mandible and hyoid bone, allowing potential extension into the anterior cervical region.^[10]^[1]

Clinical significance

Infections

Infections of the submandibular space most commonly arise from odontogenic sources, particularly involving the mandibular second and third molars, where infection penetrates the lingual cortex below the mylohyoid muscle attachment line, facilitating spread into the space.^[3]^[13] These infections often originate from untreated dental caries, periapical abscesses, or periodontal disease, with polymicrobial flora including streptococci, staphylococci, and anaerobes such as Peptostreptococcus and Prevotella species predominating.^[3] A particularly severe manifestation is Ludwig's angina, a bilateral, rapidly progressive cellulitis that involves the submandibular, sublingual, and submental spaces, often stemming from the same odontogenic foci.^[14] First described by German surgeon Wilhelm Friedrich von Ludwig in 1836, this condition presents with characteristic woody induration and elevation of the floor of the mouth, leading to trismus, dysphagia, drooling, and stridor due to potential airway compromise from expanding edema.^[15]^[14] The infection's propensity for rapid spread exploits anatomic communications between the submandibular space and adjacent fascial planes, heightening the risk of mediastinitis or vascular thrombosis if untreated.^[14] Other infections include submandibular abscesses, which form as walled-off collections from untreated cellulitis, and acute bacterial sialadenitis of the submandibular gland, typically resulting from retrograde ascent of oral bacteria into the ductal system due to salivary stasis or obstruction.^[16]^[17] Symptoms specific to submandibular involvement encompass fever, malaise, and firm, indurated swelling below the jaw that obscures mandibular palpation, often accompanied by ipsilateral pain and limited neck mobility.^[18]^[19] Management prioritizes airway protection through intubation or cricothyrotomy if necessary, followed by broad-spectrum intravenous antibiotics targeting oral flora, such as penicillin with metronidazole or clindamycin for penicillin-allergic patients.^[14] Surgical intervention via incision and drainage is essential for abscesses or extensive cellulitis, with an extraoral approach—typically a 2- to 3-cm horizontal incision along the lower border of the mandible—preferred to ensure adequate decompression while minimizing cosmetic deformity.^[18]^[20] Extraction of the offending tooth and supportive care, including hydration and analgesia, complete the acute treatment, with close monitoring to prevent complications like sepsis.^[14]

Other pathologies

Neoplasms of the submandibular gland represent 5-15% of all salivary gland tumors, with approximately 40-50% of these being malignant.^[21]^[22] The most common benign tumor is pleomorphic adenoma, accounting for a significant portion of cases, while adenoid cystic carcinoma is the most common malignant tumor in the submandibular gland, followed by mucoepidermoid carcinoma.^[23]^[24] These tumors often arise from the submandibular gland itself, which occupies much of the submandibular space.^[25] Non-infectious inflammatory conditions affecting the submandibular space include chronic sialadenitis, characterized by recurrent or persistent glandular inflammation typically due to obstruction from salivary stones or strictures.^[17] This leads to episodic swelling and pain, with the submandibular gland being the most frequently involved site owing to its anatomy and saliva composition.^[26] Autoimmune disorders such as Sjögren's syndrome can also impair submandibular gland function, resulting in lymphocytic infiltration and reduced saliva production.^[27] In Sjögren's, up to 50% of patients experience submandibular gland enlargement alongside parotid involvement.^[27] Congenital anomalies in the submandibular space are uncommon and may include cysts such as epidermoid cysts or plunging ranulas, which are mucus extravasation pseudocysts originating from the sublingual gland but extending into the space.^[28]^[29] Congenital ranulas present as soft, fluctuant masses in the floor of the mouth or neck, often appearing shortly after birth and potentially causing feeding difficulties if large.^[30] Vascular pathologies, though rare, encompass hemangiomas, of which approximately 18% occur in the submandibular region in pediatric cases, presenting as compressible masses.^[31] Pseudoaneurysms of the facial artery can also occur in this space, typically following trauma or dental procedures, forming pulsatile hematomas that mimic other swellings.^[32]^[33] Patients with these non-infectious pathologies often report a painless, slowly enlarging mass in the submandibular region, contrasting with the acute tenderness of infections; glandular issues like those in Sjögren's may additionally cause xerostomia and dry mouth.^[27]

Surgical and diagnostic considerations

Diagnostic imaging plays a crucial role in evaluating the submandibular space for infections, masses, or ductal pathologies. Computed tomography (CT) is the preferred modality for detecting abscesses, as it effectively identifies rim-enhancing fluid collections indicative of purulent processes within the space.^[34] Magnetic resonance imaging (MRI) excels in providing detailed soft tissue resolution, aiding in the characterization of tumors or inflammatory changes by delineating glandular and nodal involvement without radiation exposure.^[34] Ultrasound serves as an initial, non-invasive assessment tool for submandibular gland evaluation, particularly useful in identifying sialoliths, ductal dilatation, or superficial abscesses due to its real-time imaging capabilities and lack of ionizing radiation.^[2] Surgical access to the submandibular space typically involves an extraoral submandibular incision, a transcervical approach that allows direct exposure for drainage of abscesses or excision of the submandibular gland in cases of chronic sialadenitis or neoplasia.^[35] For malignancies with involvement of level I lymph nodes, a selective level I neck dissection is performed, encompassing submental and submandibular nodal groups while aiming to preserve non-involved structures.^[36] Intraoperative orientation relies on key landmarks such as the anterior and posterior bellies of the digastric muscle, which define the boundaries of the submandibular triangle, and the mylohyoid muscle, which separates superficial and deep glandular lobes to guide dissection.^[37] Procedural risks associated with these interventions include injury to the marginal mandibular branch of the facial nerve, potentially leading to lower lip weakness; the hypoglossal nerve, causing tongue deviation; and the facial artery or vein, resulting in hematoma formation.^[38] These complications underscore the need for meticulous dissection planes and nerve monitoring during surgery.^[39] By 2025, minimally invasive techniques such as sialendoscopy have gained prominence for managing ductal pathologies in the submandibular space, offering endoscopic visualization and intervention through the Wharton's duct to retrieve stones or dilate strictures while preserving glandular function.^[40] This approach, often performed under local anesthesia, reduces recovery time and cosmetic impact compared to traditional open surgery, with success rates exceeding 80% for proximal sialolithiasis in recent series.^[41]

References

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### Summary of Submandibular Space Details
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ANATOMY AND BOUNDARIES. The major salivary glands consist of the parotid, submandibular, and sublingual glands. Submu- cosal clusters of salivary tissue ...<|control11|><|separator|>
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