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There is a wide spectrum of clinical manifestation of COVID-19 in the head and neck, but often these do not have an imaging correlate. This review will highlight the most common imaging features of COVID-19 in the head and neck that can be seen on routine head and neck CT and MRI. In addition, situations where a more dedicated imaging protocol is required will be highlighted. Finally, as mass vaccination efforts are underway worldwide, post vaccination imaging can often complicate cancer surveillance imaging. Post vaccination imaging features and recommendations will be discussed.
Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in a wide variety of clinical manifestations in the head and neck including: anosmia, cervical and axillary adenopathy, cranial neuropathies including optic neuritis, hearing loss, xerostomia and sialadenitis, Guillain-Barrè syndrome, brachial plexopathy, and venous thrombosis. With increasing vaccination efforts worldwide, awareness of post vaccination imaging features is also important to consider when assessing patients with head and neck symptoms, or in interpreting surveillance imaging for patients with known malignancy. While clinical manifestations of COVID-19 often will not have an imaging correlate, imaging remains a valuable tool to exclude other causes not due to SARS-CoV-2 infection. Conversely, a familiarity with the wide variety of imaging manifestations of COVID-19 in the head and neck also helps to include COVID-19 in the differential diagnosis when assessing patients who present atypically and have not yet been tested for SARS-CoV-2 infection. In this review, imaging manifestations will be predominantly presented in CT and MRI modalities, as these are the mainstay of head and neck imaging.
Routine CT and MRI scans remain the best templates in our approach to presenting the manifestations of COVID-19 as they relate to the head and neck. These studies often include the posterior fossa, and to variable degree, the supratentorial and suprasellar structures. A discussion of imaging manifestations of COVID-19 that involve the brain, will provide a greater understanding of common clinical presentations of this disease.
The most common clinical neurologic manifestations of COVID-19 include encephalopathy, stroke, and encephalitis.
Encephalopathy presents as altered mental status >24 hours associated with seizure and/or focal neurologic deficits not fulfilling criteria for encephalitis with no evidence of toxic or metabolic factors.
Stroke presents clinically with sudden neurologic deficit secondary to acute vascular lesion seen on brain MRI or CT scan, in patients with transient focal neurologic deficit with normal MRI (transient ischemic attack) or in patients with cerebral venous thrombosis. In a multicenter study of 222 COVID-positive patients, the most common presenting clinical symptoms included: altered mental status, 52%; focal central neurologic deficit, 44%; peripheral limb weakness, 12%; and headache, 11%, with less common head and neck related symptoms including cranial neuropathy, 5%; anosmia, 3%; ageusia, 1.8%.
CT findings of rhombencephalitis include brainstem and cerebellar patchy hypodensity. MRI is superior to CT scan due to inherent streak artifact from the dense bone of the posterior fossa and skull base. MRI findings include T1-weighted hypointensity, T2-weighted and T2 FLAIR hyperintensity with associated diffusion-weighted restriction (Figure 1). The enhancement pattern may be linear, heterogeneous and in some cases, include ring enhancement if abscesses are present. Necrotizing rhombencephalitis is evident when these above findings are accompanied by blood products. This may manifest as hyperdensity on CT scan or blood products on the MRI scan which may yield susceptibility-weighted hypointensity on follow up imaging if acute/subacute blood products are not identified on acute presentation.
Stroke affects up to 3% of patients presenting with SARS-CoV-2 infection and up to 6% of patients admitted to the ICU.
Proposed pathogenesis in the creation of thrombi includes hypercoagulable state, cytokine storm, endotheliopathy, arterial dissection and vasculitis-like mechanism. In addition, cardiac emboli due to arrhythmias are reported in 10% of hospitalized patients and up to 40% of ICU patients.
The earliest sign of ischemic infarct on CT scan may be the so called “dense vessel” sign, which in the case of CT neck, includes vertebral or basilar artery supply to the posterior fossa. Within a few hours of stroke onset, there may be loss of differentiation between the grey matter and white matter with effacement of sulci and/or cerebellar folia. As the area of ischemia becomes more hypodense, demarcation of the infarct margin becomes more conspicuous. As the stroke progresses from the acute to subacute stage, further delineation of the stroke makes it even easier to appreciate. Ischemic stroke may become hemorrhagic over time. The MRI scan offers the advantage of evaluating the movement of water molecules in the brain tissue with diffusion weighted imaging (DWI). This will detect the earliest ischemia, prior to detection on CT Images, as the movement of water molecules in and out of brain cells is disrupted, defining the infarct core. Within hours, T2-weighted signal increases. Within 2-3 weeks, the T2-weighted signal decreases. As swelling decreases, volume loss and encephalomalacia take form, yielding a chronic infarct. Susceptibility-weighted imaging (SWI) is superior to CT in the evaluation of hemorrhagic transformation of the infarct.
Orbit: optic neuritis
Orbital manifestations of COVID-19 such as optic neuritis have been reported during the acute infection and post recovery phase.
The exact pathophysiology is unclear, and various mechanisms proposed include sequelae of proinflammatory state with hypercoagulability and cytokine storm, result of systemic abnormalities including hypoxia and severe hypertension, or direct viral invasion.
Patients may present with sudden decline in visual acuity, eye or periorbital pain, or headaches. On MR imaging, there is T2 hyperintensity in the optic nerves, which may be unilateral or bilateral. Contrast enhancement may be present as well. Optimal technique to assess this is MRI orbits with and without contrast.
Sinonasal: anosmia, olfactory bulb, mucormycosis
Anosmia and dysgeusia have been reported as common early symptoms in patients with COVID-19, occurring in greater than 80% of patients in 1 series.
Imaging findings, however, are not commonly observed. MR imaging findings may show increased T2 signal in the olfactory bulbs and tracts with or without contrast enhancement, but this has only been demonstrated in 19% of patients in 1 series.
Thin section T2-weighted and post-contrast T1-weighted coronal images through the anterior cranial fossa are optimal to demonstrate the olfactory apparatus. Targeted imaging protocols are required if this entity is suspected clinically as these sequences are not typically included on routine MRI of the brain. Other imaging findings include olfactory bulb atrophy after COVID-19 induced anosmia in patients with prolonged postinfectious anosmia. This may reflect persistent, chronic olfactory bulb injury in patients with persistent symptoms.
COVID‐19‐associated mucormycosis (CAM) is an opportunistic fungal infection seen most often in severe and critical COVID-19 patients who underwent steroid treatment for COVID-19 during the inflammatory phase of disease. Several factors have been implicated in CAM, which include glucocorticoids use, poor blood glucose control and viral‐induced lymphopenia.
A case series review revealed that most cases were reported from India (72%), affected male patients (78%), had diabetes mellitus (85%), had glucocorticoid use (85%), and had severe or critical COVID-19 (67%). The median time interval between COVID‐19 diagnosis and the first evidence of mucormycosis infection was 15 days.
About 37% of patients had mucormycosis after an initial recovery from COVID-19. Rhino‐orbital mucormycosis was most common (42%), followed by rhino‐orbito‐cerebral mucormycosis (24%) and nose and/or paranasal sinus (16%). The mortality rate was 34%, similar to non-COVID related mucormycosis.
Imaging modality of choice is MRI with contrast with complementary CT to assess bony involvement. Radiological appearances of CAM are similar to invasive fungal rhinosinusitis (Figure 3). The classic imaging feature is lack of contrast enhancement of invaded mucosa secondary to occlusion of small vessels, often referred as the “black turbinate” sign.
In disseminated and advanced craniofacial disease, non-enhancing devitalized and necrotic soft tissue at the orbits and central skull base can be seen. An important observation is that multicompartmental and extrasinonasal tissue infarction is possible without overt bone involvement, as fungal elements can disseminate from the nasal cavity via perivascular and perineural routes. Since surgery such as sinonasal debridement as an adjunct to antifungal therapy is associated with higher survival rates,
sensorineural hearing loss was found to be the most frequent audio-vestibular symptom described, occurring alone or in association with tinnitus and vertigo. IAC protocol MRI with and without contrast is the imaging modality of choice in these settings. While imaging is often negative, imaging features include CNVIII or cochlear enhancement (vestibulocochlear neuritis), intralabyrinthine enhancement (labyrinthitis), or intrinsic T1 hyperintensity of the membranous labyrinth (intralabyrinthine hemorrhage) (Figure 4).
Parotitis and xerostomia
The most common reported symptoms of COVID-19 include fever, dry cough, fatigue, muscle soreness, and headache.
As clinicians become more aware of atypical presentations, they contribute to the early detection and prevention of disease transmission. A case report describes a patient presenting 1 week prior to the ED with cough, dyspnea, and fever, with the diagnosis of COVID-19. Despite improvement of upper respiratory symptoms, she presented to another ED with symptoms of progressing parotitis and imaging findings including diffuse asymmetric swelling of unilateral parotid gland with adjacent peri-glandular fat infiltration absent sialolith, mass, infection, or abscess.
This was accompanied by progressive unilateral facial and neck swelling causing subjective malocclusion and trismus, resulting in decreased oral intake. Pertinent differential considerations include infectious parotitis, sialolithiasis, salivary gland abscess and neoplasm. Obstructing stone, mass, or abscess were excluded on the CT scan. Trismus resulted from inflammation surrounding the muscles of mastication. Free fluid may extend into surrounding anatomical neck spaces (Figure 5).
A variety of respiratory viral diseases can result in non-mumps parotitis including enteroviruses, influenza, parainfluenza, coxsackievirus, and Epstein-Barr viruses.
Viral parotitis can present with viral prodrome including flulike symptoms followed by 2-4 days of gradual swelling of both parotid glands, though unilateral involvement can be present in up to 25% of cases.
Although not seen on imaging, a brief mention of clinical xerostomia is warranted following the description of COVID-associated parotitis. Although medications and radiotherapy are the leading causes of dry mouth—due to insufficient saliva production by salivary glands—xerostomia has been reported in the literature in association with patients infected with SARS-CoV-2. Although the mechanism of alterations in saliva production in patients with COVID-19 is unclear, it is proposed that glandular infection with SARS-CoV-2 contributes to these presentations.
Angiotensin converting enzyme 2 (ACE2) receptor mediates entry of SARS-CoV-2 into the cell and ACE2 receptors were found in ductal elements of salivary glands. This provides a possible mechanism of linkage between COVID-19 patients and xerostomia.
Vaccination-associated adenopathy is an imaging finding after administration of many vaccines and is not unique to COVID-19 vaccines. However, during mass vaccination effort due to a pandemic, frequency of post vaccination adenopathy may increase
According to these recommendations, routine imaging examinations such as those for screening, should be scheduled before or at least 6 weeks after the final vaccination dose to allow for any reactive adenopathy to resolve. However, urgent clinically indicated imaging (eg, for acute symptoms, short-interval treatment monitoring, urgent treatment planning or complications) should not be delayed due to prior vaccination. The vaccine should be administered on the side contralateral to the primary or suspected cancer, and both doses should be administered in the same arm. Detailed vaccination information (eg, dates administered, injection site, laterality, and type of vaccine) should be included in patient imaging questionnaire, and this information should be made readily available to interpreting radiologists. Currently, there are no standardized system and different institutions will ask for this information depending on what type of examination is being performed, in particular those that cover the axilla, neck and chest regions. For example, at our institution, mammography, shoulder musculoskeletal or brachial plexus imaging will require detailed vaccination history. Therefore, an effective management will depend on good coordination of the referring physician, patient vaccination record, and radiologists, when managing adenopathy in the setting of COVID-19 vaccination.
Clinicians should be aware that incidental post vaccination adenopathy is more common during vaccination efforts. Vaccination should not be delayed due to upcoming imaging, and imaging should be scheduled before the first, or at least 6 weeks after, the final vaccination dose whenever possible.
The CT scan of the neck often includes the posterior fossa, the transverse and sigmoid sinuses. Oftentimes, the straight sinus, vein of Galen and cavernous sinus, and less often, portions of the high superior sagittal sinus are also included. The association between venous thrombosis in patients with COVID-19 is well documented in the literature.
This may imply that the hypercoagulability caused by SARS-CoV-2 infection may persist after the symptoms of COVID-19 resolve. There are a myriad of mechanisms by which SARS-CoV-2 is postulated to promote coagulation. First, D-dimer, fibrinogen, and fibrin degradation products are elevated relative to healthy controls.
This dense venous structure can persist for up to 1 to 2 weeks. Contrast administration is recommended when evaluating thrombosis of venous structures as it best delineates the thrombus as a filling defect within the lumen.
Catheter angiography, previously the gold standard in the evaluation of venous thrombosis, is now rarely necessary for diagnosis, supplanted by the introduction of CT and MR venography. The CT venogram of the neck and head is performed with injection of 100 mL of intravenous nonionic contrast medium (iodine, 300 mg/mL) at a rate of 3 mL/ sec with a 45-second delay between intravenous injection and the start of scanning.
Cerebral venous infarction results from thrombus propagation into draining cortical veins, causing significant extravasation of fluid into the brain resulting in vasogenic edema, focal cerebral edema and hemorrhage.
In 1 systematic review and meta-analysis of 57 patients with COVID-19, the most common locations of cerebral venous thrombosis included: transverse sinus, 65%; sigmoid sinus, 47%; superior sagittal sinus, 44%; deep and/or central vein, 37%; straight sinus, 21%; and cortical vein, 21% (sum of percentages >100% as patients may present with multiple occluded venous structures in 1 setting).
Hemorrhage secondary to cerebral venous thrombosis is related to the location of draining veins and suspected when bleeding does not correspond to arterial territories (Figure 7).
Cavernous Sinus Thrombosis
The cavernous sinus collects venous drainage intracranially and from orbits, midface, and neck. This may predispose to infection via thrombophlebitis or septic emboli. Aseptic or noninfectious cavernous sinus thrombosis includes hypercoagulable disorders such as malignancy, pregnancy, arteriovenous malformations, and inflammatory conditions such as Tolosa–Hunt syndrome. The symptoms of cavernous sinus thrombosis can overlap with other common ophthalmic presentations, such as orbital cellulitis and orbital apex syndrome. Common symptoms include ptosis, proptosis, chemosis, ophthalmoplegia (cranial nerve III, IV, VI), and loss of sensation in the ophthalmic and maxillary divisions of the trigeminal nerve (V1 and V2). Rarely, visual loss can occur in this entity due to optic nerve ischemia, retinal ischemia, and anterior ischemic optic neuropathy.
An Italian study followed 85 COVID-19 positive patients in a single hospital, treated with thromboprophylaxis on admission. Forty-three patients developed venous thromboembolism. Seven of these involved the internal jugular vein.
Guillain-Barrè syndrome (GBS) is a rare disease representing the most frequent cause of acute flaccid symmetrical weakness of the limbs and areflexia usually reaching its peak within a month. The etiology and pathogenesis remain largely enigmatic and the syndrome results in death or severe disability in 9%-17% of cases despite immunotherapy.
Guillain-Barré syndrome is diagnosed by the combination of clinical presentation, CSF study, and electrophysiological criteria. CSF abnormalities are characterized by increased protein without pleocytosis, which is a non-specific finding, seen in many of the conditions which mimic GBS on imaging and clinically. Nerve conduction abnormalities include slow or blocked nerve conduction, prolongation of distal latency, and f-waves.
CT is not the modality of choice to evaluate Guillain-Barrè syndrome as the sensitivity for the evaluation and enhancement of nervous tissues is much greater with MRI.
The lung apices are included in all CT scans of the neck, and as such a brief discussion of the lung findings in patients infected with SARS-CoV-2 presenting with COVID-19 is warranted. CT sensitivity seems to be high in patients with positive RT-PCR.
Typical CT findings in individuals with COVID-19 were ground-glass opacities, particularly on the peripheral and lower lobes, and bilateral multiple lobular and subsegmental areas of consolidation, especially in ICU patients.(Figure 9)
It is important to realize that CT is not the standard for the diagnosis of COVID-19, but its findings help suggest the diagnosis in the appropriate setting. A single-center study of 205 CT scans performed for reasons other than COVID-19 yielded incidental lung findings leading to the suspicion of COVID-19. Six patients (3%) were confirmed COVID-19 positive by RT-PCR, with the majority of patients experiencing mild to moderate symptoms.
The SARS-CoV-2 virus is a formidable infectious agent due to its ease of transmission and its potential for devastation of at-risk patient populations. Although head and neck imaging is often not performed for the purpose of COVID-19 diagnosis, abnormalities involving the anatomy described in this communication can sometimes raise the suspicion of COVID-19 if the appropriate clinical questions and testing is subsequently pursued. This combination of radiologic and clinical awareness will protect the community by identifying infected patients early and inserting them into the proper treatment regimen.
Declaration of conflict of interest
All authors declare no conflict of interests.
The authors reported no proprietary or commercial interest in any product mentioned or concept discussed in this article.
Neurologic manifestations associated with COVID-19: A multicentre registry.