Calvarial lesions are often asymptomatic and are usually discovered incidentally during computed tomography or magnetic resonance imaging of the brain. Calvarial lesions can be benign or malignant. Although the majority of skull lesions are benign, it is important to be familiar with their imaging characteristics and to recognise those with malignant features where more aggressive management is needed. Clinical information such as the age of the patient, as well as the patient’s history is fundamental in making the correct diagnosis. In this article, we will review the imaging features of both common and uncommon calvarial lesions, as well as mimics of these lesions found in clinical practice.Teaching Points • Skull lesions are usually discovered incidentally; they can be benign or malignant. • Metastases are the most frequent cause of skull lesions. • Metastatic lesions are most commonly due to breast cancer in adults and neuroblastoma in children. • Multiple myeloma presents as the classic “punched out” lytic lesions on radiographs. • Eosinophilic granuloma is an osteolytic lesion with bevelled edges.

The major and minor salivary glands of the head and neck are important structures that contribute to many of the normal physiologic processes of the aerodigestive tract. The major salivary glands are routinely included within the field of view of standard neuroimaging, and although easily identifiable, salivary pathology is relatively rare and often easy to overlook. Knowledge of the normal and abnormal imaging appearance of the salivary glands is critical for forming useful differential diagnoses, as well as initiating proper clinical workup for what are often incidental findings. The purpose of this review is to provide a succinct image-rich article illustrating relevant anatomy and pathology of the salivary glands via an extensive review of the primary literature. In Part 1, we review anatomy as well as provide an in-depth discussion of the various infectious and inflammatory processes that can affect the salivary glands.

Vascular lesions have a varied appearance and can commonly occur in the head and neck. A majority of these lesions are cutaneous and congenital; however, some may be acquired and malignant. The presentation and clinical history of patients presenting with head and neck lesions can be used to guide further imaging, which can provide important diagnostic and therapeutic considerations. This review discusses the revised International Society for the Study of Vascular Anomalies (ISSVA) classification system for vascular tumors and malformations, as well as explores the most common vascular anomalies including their clinical presentations and imaging findings.

The salivary glands are small structures in the head and neck, but can give rise to a wide variety of benign and malignant pathology. When this occurs, patients may present with palpable swelling, although it is quite common that they are asymptomatic and a salivary gland mass was discovered as an incidental finding on imaging performed for another reason. It is, therefore, critical that radiologists pay careful attention to the salivary glands and have working knowledge of the key differentiating features of the most common neoplastic and nonneoplastic etiologies of salivary gland masses. The purpose of this review is to provide a succinct image-rich article illustrating the various causes of salivary gland masses via an extensive review of the primary literature. In Part 2, we discuss neoplasms and tumor-like lesions of the salivary glands with a key emphasis on specific imaging features of the most common pathologic entities.

PurposeThe imaging of primary and metastatic brain tumours is very complex and relies heavily on advanced magnetic resonance imaging (MRI). Utilisation of these advanced imaging techniques is essential in helping clinicians determine tumour response after initiation of treatment. Many options are currently available to treat brain tumours, and each can significantly alter the brain tumour appearance on post-treatment imaging. In addition, there are several common and uncommon treatment-related complications that are important to identify on standard post-treatment imaging.MethodsThis article provides a review of the various post-treatment-related imaging appearances of brain neoplasms, including a discussion of advanced MR imaging techniques available and treatment response criteria most commonly used in clinical practice. This article also provides a review of the multitude of treatment-related complications that can be identified on routine post-treatment imaging, with an emphasis on radiation-induced, chemotherapy-induced, and post-surgical entities.Summary/ConclusionAlthough radiological evaluation of brain tumours after treatment can be quite challenging, knowledge of the various imaging techniques available can help the radiologist distinguish treatment response from tumour progression and has the potential to save patients from inappropriate alterations in treatment. In addition, knowledge of common post-treatment-related complications that can be identified on imaging can help the radiologist play a key role in preventing significant patient morbidity/mortality.Teaching points• Contrast enhancement does not reliably define tumour extent in many low-grade or infiltrative gliomas.• Focal regions of elevated cerebral blood volume (rCBV) on dynamic susceptibility contrast (DSC) perfusion-weighted imaging are suggestive of tumour growth/recurrence.• Brain tumour treatment response criteria rely on both imaging and clinical parameters.• Chemotherapeutic agents can potentiate many forms of radiation-induced injury.• Ipilimumab-induced hypophysitis results in transient diffuse enlargement of the pituitary gland.

Congenital anterior neck masses comprise a rare group of lesions typically diagnosed in childhood. Most commonly, lesions are anomalies of the thyroglossal duct, namely the thyroglossal duct cyst, along with ectopic thyroid tissue. Although usually suspected based on clinical examination, imaging can confirm the diagnosis, assess the extent, and evaluate for associated complications. Imaging characteristics on ultrasound, CT, and MRI may at times be equivocal; differential considerations include branchial cleft cyst, dermoid/epidermoid, laryngocele, thymic cyst, lymphatic malformation, and metastatic disease. Thus, understanding of the embryologic course of thyroid development is crucial with recognition of critical landmarks such as the foramen cecum, hyoid bone, thyroid cartilage, and strap musculature to aid in the diagnosis of an anterior neck mass.

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Trigeminal neuralgia is a debilitating condition with numerous etiologies. In this retrospective case series, we report a cohort of patients with a rarely described entity, absence of Meckel cave, and propose this as a rare cause of trigeminal neuralgia. A search of the electronic medical record was performed between 2000 and 2020 to identify MR imaging reports with terms including "Meckel's cave" and "hypoplasia," "atresia," "collapse," or "asymmetry." Images were reviewed by 2 blinded, board-certified neuroradiologists. Seven cases of the absence of Meckel cave were identified. Seven patients (100%) had ipsilateral trigeminal neuralgia and ipsilateral trigeminal nerve atrophy, suggesting an association between absence of Meckel cave and trigeminal neuralgia. Absence of Meckel cave is a rare entity of unknown etiology, with few existing reports that suggest the possibility of an association with trigeminal neuralgia. Its recognition may have important implications in patient management. Future studies and longitudinal data are needed to assess treatment outcomes and added risks from surgical intervention in these patients.ABBREVIATION: TN ¼ trigeminal neuralgia T rigeminal neuralgia (TN) is a debilitating condition resulting in a severely compromised quality of life in affected people. 1 It more commonly affects women and has an overall prevalence of 0.07% of the population. 2 Treatment of TN revolves around accurate identification of the potential etiology. Advances in neuroimaging, particularly MR imaging, have played a crucial role in assessing various structural causes of TN, such as neurovascular compression, compressive mass, or multiple sclerosis. 3 Depending on the suspected etiology, various treatment options may be used, including medication, neurovascular decompression, stereotactic radiosurgery, or percutaneous balloon compression.A rarely reported entity, absence of Meckel cave, has been described in a few patients with TN, including 2 case reports and 3 patient case series. [4][5][6] Most important, there are only a few reports, to our knowledge, on the absence of Meckel cave in patients other than those with TN. This retrospective study aimed to demonstrate the potential relationship of an absent Meckel cave with TN versus without TN, which may have important diagnostic and treatment implications.