What are the differential diagnoses and initial management steps for a middle-aged man presenting with hemibody pain and normal Magnetic Resonance Imaging (MRI) of the brain and cervical spine?

Differential Diagnoses for Hemibody Pain with Normal Brain and Cervical Spine MRI

In a middle-aged man with hemibody pain and normal brain and cervical spine MRI, the most critical differential to consider is spontaneous intracranial hypotension (SIH), followed by parietal cortical lesions, medullary compression, and peripheral/spinal pathology below the imaged cervical segments. 1

Primary Differential Diagnoses

Spontaneous Intracranial Hypotension (SIH)

• Normal brain and spine MRI does not rule out SIH, as this is a recognized rare finding in patients with subsequently confirmed disease. 1
• SIH can present with atypical pain patterns including hemibody distribution, particularly when associated with subdural collections or brain sagging. 1
• The imaging protocol used matters critically—ensure the MRI was reviewed by a neuroradiologist and included appropriate sequences (T2-weighted, FLAIR, T2* GRE or SWI, and pre/post-contrast 3D T1-weighted acquisitions). 1
• If high clinical suspicion persists after neuroradiologist review, refer to a specialist neuroscience center for multidisciplinary team discussion and consider up to two high-volume non-targeted lumbar epidural blood patches empirically. 1
• Subsequent investigation may require CT myelography or digital subtraction myelography to locate CSF leak sites. 1

Parietal Cortical Lesions (Pseudothalamic Pain Syndrome)

• Lesions affecting the white matter deep to the caudal insula and opercular region of the posterior parietal cortex can produce hemibody pain with a burning or "icelike" quality. 2
• This pain is typically associated with impaired pinprick and temperature sensation on the affected side. 2
• The mechanism involves thalamocortical disconnection, particularly affecting connections between the second somatosensory representation (SII) and thalamic nuclei. 2
• Standard brain MRI may miss subtle white matter lesions—consider dedicated high-resolution sequences or repeat imaging if clinical suspicion is high. 2

Medullary Compression/Vascular Compression

• Neurovascular compression of the caudal medulla by the posterior inferior cerebellar artery can cause severe hemibody pain with sensory and autonomic disturbances. 3
• This may be accompanied by ipsilateral cranial nerve dysfunction (trigeminal, cochlear, glossopharyngeal). 3
• MRI may show subtle anterolateral indentation of the medulla causing displacement—this requires careful review by an experienced neuroradiologist. 3
• Microvascular decompression can provide complete resolution of symptoms in confirmed cases. 3

Thoracic or Lumbar Spine Pathology

• The cervical spine MRI does not evaluate the thoracic or lumbar spine, where pathology could produce hemibody pain patterns, particularly if affecting the spinal cord. 4
• Consider thoracic myelopathy, which can present with bilateral symptoms and balance difficulties. 4
• MRI of the thoracic and/or lumbar spine without contrast should be obtained if clinical examination suggests lower spinal cord involvement. 4

Peripheral Vascular or Arterial Dissection

• Cervical arterial dissection can cause hemibody pain and may not be visible on standard MRI sequences. 1
• If vascular pathology is suspected, MRA of the neck without and with IV contrast should be obtained. 1
• Vertebral artery dissection is associated with foramen transversarium fractures in trauma but can occur spontaneously. 5

Critical Next Steps in Evaluation

Immediate Actions

• Ensure the existing MRI was reviewed by a neuroradiologist with specific attention to subtle findings including medullary compression, parietal white matter lesions, and signs of intracranial hypotension. 1
• Perform detailed neurological examination focusing on:
  • Sensory testing (pinprick, temperature, proprioception) to characterize the distribution and quality of sensory loss 2
  • Cranial nerve examination, particularly trigeminal, cochlear, and glossopharyngeal function 3
  • Autonomic symptoms (sweating abnormalities, temperature dysregulation) 3
  • Signs of myelopathy (hyperreflexia, Babinski sign, gait disturbance) 4

Additional Imaging to Consider

• MRI of the thoracic spine without contrast if examination suggests spinal cord involvement below the cervical level. 4
• MRA of the neck without and with IV contrast if vascular dissection is suspected. 1
• Repeat brain MRI with dedicated high-resolution sequences focusing on the parietal cortex and medulla if initial imaging was limited. 1, 2
• Consider whole spine MRI with fat-suppressed sequences (STIR) and high-resolution heavily T2-weighted 3D sequences if SIH remains suspected. 1

Specialist Referral Considerations

• Refer to a specialist neuroscience center with expertise in SIH if clinical suspicion remains high despite normal imaging. 1
• Neurosurgical consultation if medullary compression is identified, as microvascular decompression may be curative. 3
• Pain medicine consultation for consideration of empirical epidural blood patching if SIH is strongly suspected. 1

Common Pitfalls to Avoid

• Do not dismiss the diagnosis of SIH based solely on normal MRI—this is a recognized presentation requiring specialist evaluation. 1
• Do not assume all relevant pathology has been excluded with only brain and cervical spine imaging—thoracic and lumbar pathology can cause hemibody symptoms. 4
• Do not overlook subtle medullary compression or parietal white matter lesions that may require expert neuroradiologist review. 3, 2
• Recognize that degenerative findings on imaging are common in asymptomatic individuals and must be correlated with clinical symptoms—the absence of obvious pathology does not mean imaging is negative. 6, 7
• Do not delay specialist referral if "red flag" symptoms are present, including progressive neurological deficit, autonomic dysfunction, or severe refractory pain. 1, 4