What is the cause of a 6-day history of neck pain, radiating pain from under the right ear to the shoulder blade, difficulty moving the head, and mild vertigo in a patient with a recent history of a tooth infection on the right side that improved with antibiotics?

Urgent Evaluation for Deep Neck Infection or Vertebral Osteomyelitis

This patient requires immediate MRI of the cervical spine without contrast and urgent infectious disease consultation, as the temporal relationship between a treated tooth infection and persistent radiating neck pain with restricted movement raises serious concern for deep neck infection with potential extension to the cervical spine or vertebral osteomyelitis/discitis. 1, 2

Critical Red Flags Present

This case demonstrates multiple concerning features that mandate urgent investigation:

• Recent odontogenic infection is a well-established source of deep neck infections (38.8-49% of cases) and can cause hematogenous spread to the cervical spine, leading to discitis, osteomyelitis, or paraspinal abscess 3, 4
• Severe restriction of head movement ("very difficult to move head") suggests either severe mechanical nerve root compression or inflammatory/infectious process involving the cervical spine or deep neck spaces 2, 5
• Radiating pain from under right ear to shoulder blade follows a dermatomal pattern consistent with C5-C7 nerve root involvement, which could represent either mechanical radiculopathy or inflammatory compression from adjacent infection 2, 5
• Mild vertigo may indicate involvement of the upper cervical spine or vertebrobasilar insufficiency from inflammatory changes 1
• Persistence despite antibiotic treatment of the tooth infection suggests either inadequate source control or extension of infection beyond the original dental focus 4, 6

Why This Cannot Wait for Conservative Management

The American College of Radiology explicitly states that infection risk factors (including recent infection requiring antibiotics) constitute red flags requiring immediate imaging rather than conservative management 1, 2. The combination of:

• Recent treated infection in anatomic proximity
• Severe pain with marked functional limitation
• Radiating neuropathic pain pattern
• Failure to improve with treatment of presumed source

...creates a clinical picture that cannot be dismissed as simple mechanical neck pain from sleeping awkwardly 2, 7.

Specific Diagnostic Workup Required Immediately

Laboratory evaluation:

• Complete blood count with differential (looking for leukocytosis) 1, 7
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) - elevated inflammatory markers are red flags for infection or inflammatory arthritis 1, 2, 7
• Blood cultures if fever present or suspected bacteremia 3

Imaging:

• MRI cervical spine without contrast is the single most appropriate initial imaging study because it is most sensitive for detecting soft tissue abnormalities, inflammatory processes, infection (discitis/osteomyelitis), abscess formation, and nerve root impingement 1, 2, 7
• MRI is superior to CT for identifying degenerative cervical disorders, nerve root compression, and early infectious/inflammatory changes 2

Differential Diagnosis in Order of Urgency

1. Deep neck infection with potential cervical spine extension - dental infections can spread through fascial planes causing life-threatening complications including mediastinitis, respiratory compromise, and vertebral osteomyelitis 3, 4, 6

2. Vertebral osteomyelitis or discitis - hematogenous spread from dental source can seed the cervical spine, presenting with severe neck pain, restricted movement, and radicular symptoms 1, 2, 3

3. Cervical radiculopathy from acute disc herniation - the "slept funny" mechanism could represent acute disc herniation at C5-C6 or C6-C7 level causing nerve root compression, though the severity and persistence argue against simple mechanical etiology 2, 5

4. Retropharyngeal or parapharyngeal abscess - can present with neck pain, restricted movement, and referred pain to shoulder, particularly following dental infection 4, 6

Critical Management Pitfalls to Avoid

Do not assume this is simple mechanical neck pain despite the "slept on it funny" history - the temporal association with dental infection and severity of symptoms override this benign-sounding mechanism 2, 8.

Do not delay imaging pending trial of conservative therapy - the American College of Radiology is clear that red flags (recent infection, severe pain, restricted movement) mandate immediate imaging rather than the typical 6-8 week conservative trial used for uncomplicated mechanical neck pain 1, 2.

Do not order plain radiographs as initial imaging - X-rays are inadequate for evaluating soft tissue infection, early osteomyelitis, or nerve root compression; MRI is required 2, 7.

Do not interpret improvement of the tooth infection as ruling out complications - dental infections can seed distant sites hematogenously even after the primary source appears controlled with antibiotics 3, 6.

If MRI and Labs Are Normal

Only if MRI shows no infection, no significant disc herniation, and inflammatory markers are normal should this be managed as cervical radiculopathy with conservative therapy including NSAIDs, activity modification, and physical therapy, as 75-90% of mechanical cervical radiculopathy cases resolve with conservative management 2, 5. However, given the clinical presentation, serious pathology must be excluded first 1, 2.