Pathophysiology
P-I-24. Examination for somatic nerve neuropathy
体性神経障害の診断のための診察法
Diagnostic Background
- Diagnostic modalities differ slightly between T1DM and T2DM
- T2DM: perform DSPN screening tests
- T1DM: screening starts 5 years after diagnosis, then annually
Screening Structure
- DSPN (distal symmetric polyneuropathy → affects somatic nerves) screening has two parts:
- Questionnaire — medical history + symptoms
- Physical examination
Physical Examination Procedures
- Inspection: foot checked for deformities, wounds, abnormalities
- Sense of temperature: touch foot (eyes closed) with metallic (feels cold) vs plastic (less cold) probe → patient tells difference
- Pain perception: needle with blunt + sharp end → patient tells difference
- Tactile perception: touch sole at different sites → patient reports if felt
- Vibration test: device placed on the hallux → patient reports when vibration stops
- Reflex examination
Instrumental Detection
- Electroneurography (ENG): measures conduction velocity of peripheral nerves
- Histology: sample via needle biopsy
一問一答
▶When does DSPN screening begin in T1DM vs T2DM?
T1DM: 5 years after diagnosis, then annually; T2DM: screening at diagnosis.
▶What are the two parts of DSPN screening?
A questionnaire (history + symptoms) and a physical examination.
▶What is assessed during inspection of the foot in DSPN screening?
Deformities, wounds, and other abnormalities.
▶How is temperature sensation tested in DSPN examination?
Touch the foot (eyes closed) with a metallic (cold-feeling) vs plastic (less cold) probe; the patient identifies the difference.
▶How is pain perception tested in DSPN examination?
Using a needle with a blunt and a sharp end; the patient distinguishes between them.
▶How is tactile perception tested in DSPN examination?
Touch the sole at different sites; the patient reports whether each touch is felt.
▶How is the vibration test performed in DSPN examination?
A vibrating device is placed on the hallux (big toe); the patient reports when the vibration stops.
▶What instrumental test measures peripheral nerve conduction velocity?
Electroneurography (ENG).
▶How can diabetic neuropathy be confirmed histologically?
By a needle biopsy sample examined histologically.
▶Which nerves does DSPN screening specifically assess?
Somatic (sensory and motor) nerves of distal symmetric polyneuropathy.
▶Why are the patient's eyes closed during sensory testing?
To prevent visual cues, so the response reflects genuine sensory perception.
▶Why does T1DM screening start 5 years after diagnosis but T2DM at diagnosis?
T1DM onset is usually well-defined, so cumulative hyperglycemic damage takes years; T2DM is often present (undiagnosed) for years before detection, so complications may already exist.
▶Why does a metallic probe feel colder than a plastic one in temperature testing?
Metal conducts heat away from the skin faster, producing a stronger cold sensation that tests thermal perception.
▶Why is the hallux chosen for the vibration test?
It is the most distal point, where large-fiber sensory loss appears earliest in DSPN.
▶Why is regular (e.g., annual) screening important in diabetes?
Neuropathy is often painless and progressive; early detection allows foot protection and prevents ulceration/amputation.
▶What does electroneurography reveal in diabetic neuropathy?
Slowed nerve conduction velocity, indicating demyelination/axonal damage of peripheral nerves.
▶Why combine a questionnaire with physical examination in DSPN screening?
Symptoms (questionnaire) and objective deficits (exam) complement each other, improving detection sensitivity.
▶Why is reflex examination part of somatic nerve testing?
Loss of reflexes (e.g., ankle jerk) is an objective sign of peripheral nerve dysfunction in DSPN.
▶What multiple sensory modalities are assessed in the DSPN physical exam?
Temperature, pain, tactile (light touch), and vibration sensation, plus reflexes.
▶Why test several different sensory modalities rather than just one?
Different nerve fiber types carry different modalities; testing several detects damage that a single test might miss.