Fig. 6.44 A-F Cranial and cerebral coccidioidomycosis. A, B Multiple well-circumscribed lytic defects in the skull. C Increased uptake of 99 mTc-methylene diphosphonate in bony lesions in the skull: some of these may not be suspected clinically or on radiographs. D CT scan showing hydrocephalus associated with coccidioidal meningitis. E Basal meningeal thickening seen at autopsy. F Post contrast enhancement in the basal meninges in coccidioidomycosis. (A-D, F courtesy of Dr. J. P. McGahan, et al and AIR, 1981)

Healing is by fibrosis, often with residual bronchiectasis and in some patients, parenchymal and nodal Y calcifications. The imaging pattern of pulmonary coccidioidomycosis closely mimics that of tuberculosis (Fig. 6.43) and histoplasmosis: the distinction can often only be made by histopathology. All three infections can be complicated by other fungi (e. g., the formation of fungus balls in the cavities), and also by pyogenic secondary infection.

Extrapulmonary coccidioidomycosis can be fatal. It may occur when the patient is apparently recovering from the initial infection. Bone lesions occur in about 20% of patients with disseminated disease; the most common sites are the vertebrae, skull, pelvis, hands, feet and the ends of the long bones (Fig. 6.44 A-C, 6.45, 6.46). As occurs in many other fungal infections, such as blastomycosis, sporotrichosis, and madura mycosis, the foci of osteomyelitis are often juxta-articular. Joint infection usually follows spread from a nearby bone lesion and is most common in the wrist, elbow, and ankle. In infants, the mid shaft of bones may be affected. The bone foci are usually sharply marginated and
punched out; they are lytic at first, but later become sclerotic. Coccidioidomycosis in bones and joints is quite destructive and resembles tuberculosis or even malignancy.

A paravertebral abscess may develop from a spinal lesion and there may be complete obstruction on myelography: involvement of the intervertebral disc is infrequent. Scintigraphy is useful when dissemination is first suspected, because many bone lesions will be clinically silent for some time. CT is helpful in the spine in demonstrating the exact extent of the vertebral involvement and any abscess. MRI is useful to show an abscess and any involvement of the spinal cord.

Cerebral coccidioidomycosis causes granulomatous thickening of the leptomeninges (Fig. 6.44 E). Arteritis is an uncommon complication. CT demonstrates diffuse leptomeningitis in most patients with cerebral coccidioidomycosis. This is characterized by obliteration of the CSF spaces, particularly at the base around the mid brain: when actively infected, there will be contrast enhancement of the meninges, particularly around the brain stem (Fig. 6.44 F). Hydrocephalus complicates the infection in about 50% of the patients (Fig. 6.44D) even when the meningitis has been treated. Granulomas within the brain are uncommon, but seem to have a predilection for the cerebellum. They may be demonstrated by CT or MRI as discrete, peripheral, enhancing masses. Encephalomalacia may follow treatment, particularly after amphotericin-B-methyl ester. The most important reasons for cerebral scanning are to establish the pattern of meningeal infection, and to monitor the hydrocephalus and its response to treatment. Only occasionally will an intracerebral granuloma be of clinical importance.

Abdominal coccidioidomycosis is quite common but difficult to recognize unless the patient is known to have the infection. Lymphadenopathy (Fig. 6.47) occurs often and is recognized by radionuclide scanning, ultrasonography, CT, or MRI. About half the patients with disseminated disease will have liver involvement, which may not be clinically apparent. Radionuclide scanning of the liver shows diffuse patchy uptake and all methods of scanning can show focal lesions. Similarly, the spleen is often involved, with small, 1- to 3-mm, focal granulomas. Renal infections are usually in the parenchyma, with calyceal swelling and distortion of the collecting system: this closely resembles tuberculosis and can be demonstrated by ultrasonography, CT, MRI, or radionuclide scanning. Abdominal abscesses occur, but the imaging findings are very nonspecific.