Diabetic Mononeuropathy Multiplex
This diabetic patient presenting with asymmetric numbness starting in one foot and sequentially spreading to one lower extremity then one upper extremity has diabetic mononeuropathy multiplex, not the typical distal symmetric polyneuropathy.
Why This Pattern Indicates Mononeuropathy Multiplex
The key distinguishing feature is the asymmetric, sequential involvement of individual nerves or nerve territories, rather than the classic "glove and stocking" distribution of distal symmetric polyneuropathy 1, 2. This pattern results from ischemic infarction of the vasa nervosa (blood vessels supplying individual nerves) 3.
Diagnostic Confirmation
Perform a focused neurologic examination including:
- Pinprick sensation testing to assess small fiber function 1, 2
- Vibration perception using a 128-Hz tuning fork to evaluate large fiber function 1, 2
- Ankle reflexes to detect large fiber neuropathy 1
- Temperature sensation testing for small fiber assessment 2
The examination will reveal deficits in the distribution of specific affected nerves rather than a symmetric distal pattern 1.
Critical Differential Diagnoses to Exclude
Before confirming diabetic mononeuropathy multiplex, rule out:
- Entrapment neuropathies (carpal tunnel, ulnar nerve compression) 1, 3
- Vitamin B12 deficiency 1, 2
- Hypothyroidism-related neuropathy 1, 2
Order laboratory tests including vitamin B12 level, thyroid function tests, renal function tests, complete blood count, and serum protein electrophoresis 2.
Management Strategy
Glycemic Control
Optimize glycemic control gradually to prevent progression, but avoid rapid HbA1C reduction which can paradoxically worsen neuropathy 1.
Vascular Risk Factor Management
Aggressively manage cardiovascular risk factors including blood pressure and lipids, as mononeuropathy multiplex results from underlying vascular insufficiency 1.
Pain Management (If Present)
If neuropathic pain develops, initiate first-line pharmacotherapy immediately with:
- Pregabalin (FDA-approved, 100-200 mg three times daily) 1, 2, 4
- Duloxetine (FDA-approved first-line agent) 1, 2
- Gabapentin (alternative first-line option) 1, 2
These medications provide symptomatic pain relief but do not restore sensation 5.
Preventive Measures
- Daily foot inspection by the patient to identify early injury 1
- Annual 10-g monofilament testing to monitor progression and identify areas at risk for ulceration 1, 2
- Podiatry referral for regular foot care and proper footwear assessment 1
Common Pitfall to Avoid
Do not assume this is typical distal symmetric polyneuropathy based solely on the diabetes diagnosis. The asymmetric, sequential pattern of nerve involvement is pathognomonic for mononeuropathy multiplex and requires different prognostic counseling, as it results from focal vascular events rather than diffuse metabolic injury 1, 3.