Follow-up of advanced diabetic neuropathy

A Novel Diagnostic Test for End-Stage Sensory Failure Associated With Diabetic Foot Ulceration: Proof-of-Principle Study

BACKGROUND

Diabetic foot ulceration (DFU) affects only a subgroup of patients with diabetic neuropathy, that is, those with pain-insensitivity due to end-stage sensory failure. Pain perception failure develops insidiously and remains asymptomatic until first DFU. As loss of pain perception is clinically significant, timely detection is mandatory.

OBJECTIVES

A novel suprathreshold pinprick pain stimulus of 512 mN force made from optical glass-fiber was explored in a prospective cross-sectional diagnostic accuracy study to detect DFU-related end-stage sensory failure.

METHODS

A total of 116 participants were studied (25 healthy people, 22 patients with diabetes without relevant complications, 19 patients with previous painful foot or leg injuries, and 50 patients with previous or active painless DFU [reference standard]). Palmar and plantar surfaces were stimulated in a standardized fashion. At the feet, the second and third toe skinfolds and the middle of the plantar arch were stimulated. Participants scored stimulated pricking discomfort or pain intensity 0 to 10 on a numerical rating scale.

RESULTS

At hands, intensity was rated on average 5 (1-10) [median (range)] by 114/116 participants. Per foot, participants without DFU scored 5 (1-10), while those with DFU scored 0 (0-3) (P < .0001). At plantar toe skinfolds, the absence of pinprick pain perception detected DFU-associated sensory failure with an accuracy of 99.5% (sensitivity 99.5%, specificity 99.4%, positive likelihood ratio 248, and negative likelihood ratio 0.005).

CONCLUSION

In this pilot study, nociceptive stimulation of a plantar toe skinfold with a 512 mN optical glass-fiber pinprick accurately identified DFU-associated end-stage sensory failure.

Follow-up in transthyretin familial amyloid polyneuropathy: Useful investigations

Patients with transthyretin amyloid polyneuropathy (TTR-FAP) and asymptomatic mutation-carriers have to be regularly followed-up in order to identify disease progression and the time point for starting or modifying therapy. In this case series we describe the potential suitability of different variables as progression markers. We retrospectively analyzed the follow-up charts of 10 TTR-FAP patients. Clinical examination included the Neuropathy Impairment Score of Lower Limb (NIS-LL), temperature perception thresholds, nerve conduction and autonomic function tests. The NIS-LL had the greatest value for a sensitive and correct follow-up for all TTR-FAP stages. All other examinations provided useful additional information but they were either less suited for advanced TTR-FAP, or had a higher test-retest variability. The results of this study provide preliminary evidence that a good clinical investigation is mandatory in TTR-FAP follow-up. Simple neuropathy scores like the NIS-LL might be as useful as technical investigations for TTR-FAP follow-up.

[Alpha-lipoic acid in the treatment of diabetic polyneuropathy]

The issues of classification, pathogenesis, pathomorphology and treatment of diabetic polyneuropathy (DPN) are addressed. Pathogenetic mechanisms of the action of alpha-lipoic acid in treatment of DPN are justified. The authors present the results of randomized placebo-controlled trials of alpha-lipoic acid that revealed the high clinical efficacy and absence of side-effects even during the long-term treatment.

Transthyretin familial amyloid polyneuropathy (TTR-FAP): Parameters for early diagnosis

BACKGROUND

Familial transthyretin amyloidosis is a life-threatening disease presenting with sensorimotor and autonomic polyneuropathy. Delayed diagnosis has a detrimental effect on treatment and prognosis. To facilitate diagnosis, we analyzed data patterns of patients with transthyretin familial amyloid polyneuropathy (TTR-FAP) and compared them to polyneuropathies of different etiology for clinical and electrophysiological discriminators.

METHODS

Twenty-four patients with TTR-FAP and 48 patients with diabetic polyneuropathy (dPNP) were investigated (neurological impairment score NIS; neurological disability score NDS) in a cross-sectional design. Both groups were matched for gender and presence of pain. Quantitative sensory testing (QST), sympathetic skin response (SSR), heart rate variability (HRV), and nerve conduction studies (NCV) were performed. Both groups were compared using univariate analysis. In a stepwise discriminant analysis, discriminators between both neuropathies were identified. These discriminators were validated comparing TTR-FAP patients with a cohort of patients with chemotherapy-induced polyneuropathy (CIN) and chronic inflammatory demyelinating neuropathy (CIDP).

RESULTS

TTR-FAP patients scored higher in NDS and NIS and had impaired cold detection (CDT, p = .024), cold-warm discrimination (TSL, p = .019) and mechanical hyperalgesia (MPT, p = .029) at the hands, SSR (upper limb, p = .022) HRV and ulnar and sural NCS (all p < .05) were more affected in TTR-FAP. Ulnar nerve sensory NCV, CDT, and the MPT but not the other parameters discriminated TTR-FAP from dPNP (82% of cases), from CIN (86.7%) and from CIDP (68%; only ulnar sNCV).

CONCLUSION

Low ulnar SNCV, impaired cold perception, and mechanical hyperalgesia at the hands seem to characterize TTR-FAP and might help to differentiate from other polyneuropathies.

Temperature threshold testing: a systematic review

The diagnosis of small fiber neuropathy (SFN) has been recently defined as typical symptoms due to small nerve fiber dysfunction accompanied by reduced intra-epidermal nerve fiber density (IENFD) or abnormal temperature threshold testing (TTT). Guidelines have been published for the assessment of IENFD. However, international guidelines for TTT are lacking. This paper presents a systematic literature review on reported TTT methods and provides recommendations for its future use in studies evaluating patients. A total of 164 papers fulfilled pre-defined requirements and were selected for review. Over 15 types of instruments are currently being used with a variety of methodological approaches for location, stimulus application, and sensation qualities examined. Consensus is needed to standardize the use of TTT as a diagnostic and follow-up tool in patients.

Evaluation of the autonomic nervous system using the FAN device -- range of normal and examples of abnormal

Different components of the autonomic nervous system may be affected by different disorders to varying degrees. The aim of this study is to report first experiences with a new device (FAN®, Schwarzer, Germany) which measures heart rate variability (HRV), sympathetic skin responses (SSR) and the pulse wave transit time (PTT). We examined 190 healthy volunteers (102 men, 88 women) and in 89 subjects (46 men, 43 women) PTT during VM was investigated. In a subset of 24 subjects PTT was compared to conventional blood pressure recording. Thereafter, normal data were compared to patients with polyneuropathy (PNP) and Parkinson syndromes. All parameters of HRV decreased with age. 6 parameters for HRV at rest, during deep respiration and the valsalva ratio were reclassified into three age categories: under 40 (n=96), 40 – 60 (n=71) and 60 or older (n=23). Applying the lower limits of normal (5%-tile) subjects did not have more than 2 of these 6 parameters in the pathological range PTT reduction during phase IV of the valsalva manoeuvre was greater than 7.7 ms (5%-tile) but not age dependent. Patients with PNP had reduced HRV and SSR, Parkinson patients had more frequently impaired blood pressure regulation according to PTT assessment. Our investigation shows that the FAN® might be useful for clinicians to detect autonomic disorders.

Gender differences in the onset of diabetic neuropathy

OBJECTIVE

Diabetic neuropathy is one of the more common complications plaguing individuals with type 2 diabetes. The development and progression of such complications are responsible for much of the morbidity and mortality related to this disease. Few studies have evaluated age at onset of diabetic neuropathy between genders. A difference in the progression of diabetic neuropathy between men and women may exist. This investigation evaluated gender differences in the age at onset of neuropathy among patients with type 2 diabetes.

METHODS

The study, a retrospective chart analysis, reviewed 376 inpatient and outpatient medical records between January 2004 and January 2006 from a Cleveland, Ohio, hospital. Onset of neuropathy was determined by the date the neuropathy International Classification of Diseases, Ninth Revision code was first included in the medical chart; for this study, onset was equated with the date of first identification. Data were analyzed via a tailed independent t test.

RESULTS

Of the 376 inpatient and outpatient charts reviewed, 156 were for male patients and 220 were for female patients (41% and 59%, respectively). All patients had type 2 diabetes; however, 23% (n=86) required insulin therapy at the time of the study. Males developed neuropathic complications at 63 years, approximately 4 years earlier than did females (at 67 years). The t test revealed a statistically significant difference in age at onset of diabetic neuropathy between the male and female subjects.

CONCLUSIONS

This study demonstrates that the males in the study population developed neuropathy earlier than did the females. It may then be hypothesized that earlier interventions in the male population may improve disease outcomes.

Evaluation of atrophy of foot muscles in diabetic neuropathy – A comparative study of nerve conduction studies and ultrasonography

OBJECTIVE

To evaluate the relation between the findings at nerve conduction studies and the size of small foot muscles determined by ultrasonography.

METHODS

In 26 diabetic patients the size of the extensor digitorum brevis muscle (EDB) and of the muscles between the first and second metatarsal bone (MIL) was determined. Motor nerve conduction studies of the peroneal and tibial nerves were performed with determination of the amplitudes of the CMAPs and of the nerve conduction velocities (NCV). Further, a standardised clinical examination was performed providing a neurological impairment score.

RESULTS

Seventeen patients fulfilled the criteria for diabetic neuropathy. The cross-sectional area of the EDB muscle and the thickness of the MIL muscle were 116 +/- 65 mm2 and 29.6 +/- 8.2 mm, respectively. Close relations were established between muscle size and the amplitude of the CMAP of the peroneal (r=0.77, p<0.001) and of the tibial nerve (r=0.70, p<0.01). Further there were close relations between the muscle size and the NCV of the peroneal (r=0.62, p<0.01) and of the tibial nerve (r=0.71, p<0.001).

CONCLUSIONS

The amplitude of the CMAP of the peroneal and of the tibial nerves is closely related to the size of the small foot muscles as determined by ultrasonography.

SIGNIFICANCE

In diabetic patients motor nerve conduction studies can reliably determine the size of small foot muscles.