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Opportunistic Infections


KEY FACTS

Terminology

  • Infection in setting of immunocompromised state

    • HIV(+)

    • Chronic/systemic illness

    • Steroid therapy

    • Cancer ± chemotherapy

Imaging

  • CT → define osseous involvement

  • MR → evaluate extent of intramedullary, intradural extramedullary, and extradural involvement

  • Discitis/osteomyelitis → loss of disc height, bony endplate erosive changes

    • Enhancement of irregular adjacent endplates, blurring of dark cortical margin of endplates

  • Epidural abscess/phlegmon → soft tissue in ventral/dorsal extradural space

    • Homogeneous enhancement of phlegmon

    • Rim enhancement of abscess

  • Paraspinal abscess/phlegmon

  • Infectious arachnoiditis → thickening, clumping of nerve roots

  • Intramedullary abscess → peripherally enhancing intramedullary lesion

Top Differential Diagnoses

  • Osteomyelitis, pyogenic

  • Meningitis, spinal

  • Acute disseminated encephalomyelitis, spinal cord

  • Acute transverse myelitis, idiopathic

Clinical Issues

  • Fever

  • Back/neck pain

  • Paraparesis

  • Treatment targeted to pathogen

Diagnostic Checklist

  • Consider complete neuraxis imaging if immunocompromised patients develop neurologic symptoms

Sagittal T1WI C+ MR (L) shows an intramedullary enhancement
in the lower thoracic cord representing toxoplasma lesion. On the sagittal T2WI MR (R), abnormal hyperintense signal extends across multiple segments
.

Axial T1WI C+ MR demonstrates a nodular enhancing intramedullary lesion
, which represents toxoplasma abscess of the spinal cord. The cord is slightly swollen. Spinal toxoplasmosis has only been described in HIV patients with simultaneously present cerebral toxoplasmosis.

Sagittal T1WI C+ MR in this case of CMV polyradiculopathy illustrates mild thickening of the proximal cauda equina and avid pial and cauda equina enhancement
.

Axial T1WI C+ MR depicts diffuse cauda enhancement due to CMV radiculitis
. The multiple root involvement with relatively smooth enhancement suggests CMV infection. Cerebrospinal fluid spread of tumor, lymphoma, and pyogenic meningitis can give a similar pattern but tends to be more nodular.

TERMINOLOGY

Definitions

  • Infection in setting of immunocompromised state

    • HIV+

    • Chronic illness, systemic infection

    • Corticosteroid therapy

    • Cancer ± chemotherapy

IMAGING

General Features

  • Best diagnostic clue

    • Intramedullary, intradural extramedullary, or extradural involvement

    • Additional systemic manifestations, such as pulmonary disease

CT Findings

  • Discitis/osteomyelitis → loss of disc height, bony endplate erosive changes

    • Enhancement of irregular adjacent endplates

    • ± enhancement of intervertebral disc

  • Epidural abscess/phlegmon → hyperdense collection in ventral/dorsal extradural space

    • Homogeneous enhancement of phlegmon

    • Rim enhancement of abscess

  • Paraspinal abscess → hyperdense collection involving paravertebral soft tissues

    • Homogeneous enhancement of phlegmon

    • Rim enhancement of abscess

  • Infectious arachnoiditis → thickening, clumping of nerve roots

    • Avid enhancement of nerve roots

  • Intramedullary abscess → peripherally enhancing intramedullary low-density lesion

    • Surrounding edema

    • Cord expansion

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