Introduction

The term suboccipital region is used to denote the area formed by the occipital condyles, upper cervical vertebrae-C1 and C2, cranio-cervical ligaments, and joints, including the craniovertebral joints (atlanto-occipital joint, median atlantoaxial joint [Cruveilhier’s joint], and lateral atlantoaxial joints). Its peculiar anatomy is a unique part of the human skeleton that provides functional support and high mobility of the head, while protecting the elements of the central nervous system and large vascular formations.

Infectious lesions in this region are also unique in their presentation and management. Infection may affect simultaneously the articulations of the occipital bone with the atlas from one or both sides, and the articulations of the atlas with the axis or the bones per se. Destruction of any element of this unified anatomic and functional system has an impact on the entire region and results in atlanto-occipital or atlantoaxial instability and subluxation, including basilar impression. The proximity of the medulla oblongata and cranial parts of the spinal cord determine the risk of neurologic complications that may be life threatening.

Early diagnosis and appropriate treatment are of paramount importance to prevent the development of potential life-threatening com plications. As in osteomyelitic lesions of other locations, infection in the suboccipital region may be caused by specific bacterial flora, tuberculosis, or mycotic agents. ¹ – ⁷ These infections can occur de novo or may be associated with a compromised immune system as well as with the pathology of the oral cavity or from the adjacent ear, nasal, and pharyngeal regions. ⁵ , ⁸ , ⁹

Tuberculosis of the craniovertebral junction (CVJ) has been more commonly reported than other infective organisms. ¹ – ⁴ , ⁶ , ⁷ , ⁹ Tuberculosis in the suboccipital region is one of the rarest and most severe conditions in bones and joints; it occurs in only 0.3 to 1.0% of patients with tuberculosis spondylitis. ² , ¹⁰ – ¹⁸ Similar to osseous tuberculous lesions in other parts of the body, suboccipital lesion can be associated with other locations of tuberculosis (commonly from the lungs, gastrointestinal viscera, kidneys, and lymph nodes) with an incidence ranging from 3 to 41%. ¹⁶

Clinical Manifestations and Complications

The specific features and clinical manifestations of craniovertebral (suboccipital) osteomyelitis depend on the anatomic peculiarities of the affected zone and the etiology of the infection ( Table 12.1 ). Upper neck pain and occipital pain, which sometimes can be described as occipital neuralgia, are usually present, and the pain is typically worsened by movements of the head, especially by rotation and bending. In cases of suboccipital tuberculosis, axial neck pain is present in 98%, stiffness of the neck muscles in 82%, and dysphagia due to prevertebral abscesses in 77%. ¹⁶ Rarely, submandibular swelling can be evident due to retropharyngeal abscesses. General inflammatory symptoms, such as fever, sepsis, and weakness, are more characteristic of acute nonspecific osteomyelitis, whereas in granulomatous infections the symptoms are malaise, weight loss, and loss of appetite.

Severe neurologic complications, such as complete or incomplete quadriplegia, dyspnea, are rare due to the large reserved space for the spinal cord in the craniocervical spinal canal. These complications can rarely result from large epidural abscesses that compress the spinal cord or the caudal part of the medulla oblongata along with cranio-cervical instability.

The assessment of functional dependence or disability is of importance in deciding the choice of treatment (conservative a or combination of conservative and surgical methods) and in achieving a successful outcome. The grades of disability in suboccipital osteomyelitis are as follows: grade I, moderate cervical pain and complete independence; grade II, limited disability and preserved functional motion and breathing ability; grade III, partial dependence on assistance; grade IV, complete dependence on assistance, with severe myelopathy and breathing difficulties. ⁴ , ⁶ , ¹⁰ , ¹⁵ , ¹⁹

Imaging Methods

Given the specific anatomy of the suboccipital region, plain films ( Fig. 12.1a,b ), which were generally used in the past, are currently used only for a preliminary analysis of the pathology. The main visualization methods are computed tomography (CT) ( Fig. 12.1c–f ) and magnetic resonance imaging (MRI) ( Fig. 12.1g,h ).

Because of the complex osseous anatomy of the craniovertebral junction, CT is ordered with a low threshold in patients with suspected CVJ infection. Multiplane CT reconstructions including three-dimensional (3D) CT are highly informative not only for visualization of the bony structures of the craniovertebral zone, but also for detailing the features of destruction (superficial, focal, or subtotal) and their sequelae, including atlas-occipital or atlantoaxial dislocations. Destruction of the lateral atlas mass has been noted to occur in 48% of suboccipital tuberculosis cases and C1-C2 subluxation in 68%. ¹⁶ Asymmetric bone lesions and irregular destruction are typical for osteomyelitis (in contrast with rheumatoid arthritis). The abscesses can be diagnosed on CT based on the widening of the prevertebral (retropharyngeal) tissues and epidural masses.

Magnetic resonance imaging is the method of choice for visualizing soft tissue, the changes in the spinal cord, the structure of the abscesses, and their extension. MRI is highly useful for early diagnosis of inflammatory bone marrow edema and arthritis, but it is less informative for detailed analysis of bone destruction when compared with CT.

Positron emission tomography (PET) CT aids in diagnosis, in particular when the process is of a slow course and with minimal destruction, but it does not help in differentiating between an inflammatory cause and an infectious process. ⁵

Magnetic resonance imaging and angio-CT aid in visualizing the vertebral artery and its involvement by abscesses or soft tissue inflammation, which is important in decreasing the risk of damaging the artery during surgery.