PERIPHERAL & DIABETIC NEUROPATHY

A FOUR PART SERIES

Charles Laudadio, MD, MBA, BSEE

“Diabetes-Related Amputations on the Rise”
-- The number of lower limb amputations in people with diabetes has climbed from 67,000 to 86,000 in just 2 years, according to the latest national health data. 

Diabetic Neuropathy is a very serious disease that usually goes undetected until it has progressed to a more serious and painful problem.  Most medical professionals do not look for neuropathy with their diabetic patients unless there is a compliant from the patient.  Yet there are tools we can use to detect neuropathy before it becomes a problem

This feature is Part 4 of the series and will conclude today with a study that you can participate in, to detect sub-clinical neuropathy.

Part 4

How Do Doctors Diagnose Diabetic Neuropathy?

How Is Diabetic Neuropathy Usually Treated?

Why Is Good Foot Care Important for People with Diabetic Neuropathy?

Are There Any Experimental Treatments for Diabetic Neuropathy?

Overview of new device

Studies on new device

New study for your participation with new device.

How Do Doctors Diagnose Diabetic Neuropathy?

A doctor diagnoses neuropathy based on symptoms and a physical exam.  During the exam, the doctor may check muscle strength, reflexes, and sensitivity to position, vibration, temperature, and light touch.  Sometimes special tests are also used to help determine the cause of symptoms and to suggest treatment.

There are some simple screening tests to check sensation that can be done in the doctor's office.  One device, the Tacticon ™, is a small, hand held, passive medical device that the FDA has recently allowed to be marketed to screen patients for evidence of subclinical peripheral neuropathy of the fingers and toes. The Tacticon ™ permits quantitative sensory testing (QST) as recommended by the American Diabetes Association Consensus Panels on Diabetic Peripheral Neuropathy.  This device can be ordered from: RX 4 Better Health by emailing your contact information to publisher@diabetesincontrol.com.

Another simple device for screening that does not provide the same degree of quantification as the Tacticon are the nylon filaments mounted on a small wand.  The filament delivers a standardized 10-gram force when touched to areas of the foot.  Patients who cannot sense pressure from the filament have lost protective sensation and are at risk for developing neuropathic foot ulcers.  Physicians may order the filament (with instructions for use) free from the Gillis W.  Long Hansen's Disease Center, LEAP Program, 5445 Point Clair Road, Carville, Louisiana 70721; telephone (504) 642-4714.

Nerve conduction studies check the flow of electrical current through a nerve.  With this test, an image of the nerve impulse is projected on a screen as it transmits an electrical signal.  Impulses that seem slower or weaker than usual indicate possible damage to the nerve.  This test allows the doctor to assess the condition of all the nerves in the arms and legs.

Electromyography (EMG) is used to see how well muscles respond to electrical impulses transmitted by nearby nerves.  The electrical activity of the muscle is displayed on a screen.  A response that is slower or weaker than usual suggests damage to the nerve or muscle.  This test is often done at the same time as nerve conduction studies.

Ultrasound employs sound waves. The sound waves are too high to hear, but they produce an image showing how well the bladder and other parts of the urinary tract are functioning.

Nerve biopsy involves removing a sample of nerve tissue for examination.  This test is most often used in research settings.

If your doctor suspects autonomic neuropathy, you may also be referred to a physician who specializes in digestive disorders (gastroenterologist) for additional tests.

How Is Diabetic Neuropathy Usually Treated?

Treatment aims to relieve discomfort and prevent further tissue damage.  The first step is to bring blood sugar under control by diet and oral drugs or insulin injections, if needed, and by careful monitoring of blood sugar levels.  Although symptoms can sometimes worsen at first as blood sugar is brought under control, maintaining lower blood sugar levels helps reverse the pain or loss of sensation that neuropathy can cause.  Good control of blood sugar may also help prevent or delay the onset of further problems.

Another important part of treatment involves special care of the feet, which are prone to problems.

A number of medications and other approaches are used to relieve the symptoms of diabetic neuropathy.

Relief of Pain

For relief of pain, burning, tingling, or numbness, the doctor may suggest an analgesic such as aspirin or acetaminophen or anti-inflammatory drugs containing ibuprofen.  Nonsteroidal anti-inflammatory drugs should be used with caution in people with renal disease.  Antidepressant medications such as amitriptyline (sometimes used with fluphenazine) or nerve medications such as carbamazepine or phenytoin sodium may be helpful.  Codeine is sometimes prescribed for short-term use to relieve severe pain.  In addition, a topical cream, capsaicin, is now available to help relieve the pain of neuropathy.

The doctor may also prescribe a therapy known as transcutaneous electronic nerve stimulations (TENS).  In this treatment, small amounts of electricity block pain signals as they pass through a patient's skin.  Other treatments include hypnosis, relaxation training, biofeedback, and   acupuncture.  Some people find that walking regularly or using elastic stockings helps relieve leg pain.  Warm (not hot) baths, massage, or an analgesic ointment such as Ben Gay may also help

Gastrointestinal Problems

Indigestion, belching, nausea or vomiting are symptoms of gastroparesis.  For patients with mild symptoms of slow stomach emptying, doctors suggest eating small, frequent meals and avoiding fats.  Eating less fiber may also relieve symptoms.  For patients with severe gastroparesis, the doctor may prescribe metoclopramide, which speeds digestion and helps relieve nausea.  Other drugs that help regulate digestion or reduce stomach acid secretion may also be used or erythromycin may be prescribed.  In each case, the potential benefits of these drugs need to be weighed against their side effects.

To relieve diarrhea or other bowel problems, antibiotics or clonidine HCL, a drug used to treat high blood pressure, are sometimes prescribed.  The antibiotic tetracycline may be prescribed.  A wheat-free diet may also bring relief since the gluten in flour sometimes causes diarrhea.

Neurological problems affecting the urinary tract can result in infections or incontinence.  The doctor may prescribe an antibiotic to clear up an infection and suggest drinking more fluids to prevent further infections.  If incontinence is a problem, patients may be advised to urinate at regular times (every 3 hours, for example) since they may not be able to tell when the bladder is full.

Dizziness, Weakness

Sitting or standing slowly may help prevent light-headedness, dizziness, or fainting, which are symptoms that may be associated with some forms of autonomic neuropathy.  Raising the head of the bed and wearing elastic stockings may also help.  Increased salt in the diet and treatment with salt-retaining hormones such as fludrocortisone are other possible approaches.  In certain patients, drugs used to treat hypertension can instead raise blood pressure, although predicting which patients will have this paradoxical reaction is difficult.

Muscle weakness or loss of coordination caused by diabetic neuropathy can often be helped by physical therapy.

Urinary and Sexual Problems

Nerve and circulatory problems of diabetes can disrupt normal male sexual function, resulting in impotence.  After ruling out a hormonal cause of impotence, the doctor can provide information about methods available to treat impotence caused by neuropathy.  Short-term solutions involve using a mechanical vacuum device or injecting a drug called a vasodilator into the penis before sex.  Both methods raise blood flow to the penis, making it easier to have and maintain an erection.  Surgical procedures, in which an inflatable or semirigid device is implanted in the penis, offer a more permanent solution.  For some people, counseling may help relieve the stress caused by neuropathy and thereby help restore sexual function.

In women who feel their sexual life is not satisfactory, the role of diabetic neuropathy is less clear.  Illness, vaginal or urinary tract infections, and anxiety about pregnancy complicated by diabetes can interfere with a woman's ability to enjoy intimacy.  Infections can be reduced by good blood glucose control.  Counseling may also help a woman identify and cope with sexual concerns.

Why Is Good Foot Care Important for People with Diabetic Neuropathy?

People with diabetes need to take special care of their feet.  Neuropathy and blood vessel disease both increase the risk of foot ulcers.  The nerves to the feet are the longest in the body, and are most often affected by neuropathy.  Because of the loss of sensation caused by neuropathy, sores or injuries to the feet may not be noticed and may become ulcerated.

At least 15 percent of all people with diabetes eventually have a foot ulcer, and 6 out of every 1,000 people with diabetes have an amputation.  However, doctors estimate that nearly three quarters of all amputations caused by neuropathy and poor circulation could be prevented with careful foot care.

To prevent foot problems from developing, people with diabetes should follow these rules for foot care:

·        Check your feet and toes daily for any cuts, sores, bruises, bumps, or infections--using a mirror if necessary.

·        Wash your feet daily, using warm (not hot) water and a mild soap.  If you have neuropathy, you should test the water temperature with your wrist before putting your feet in the water.  Doctors do not advise soaking your feet for long periods, since you may lose protective calluses.  Dry your feet carefully with a soft towel, especially between the toes.

·        Cover your feet (except for the skin between the toes) with petroleum jelly, a lotion containing lanolin, or cold cream before putting on shoes and socks.  In people with diabetes, the feet tend to sweat less than normal.  Using a moisturizer helps prevent dry cracked skin.

 

·        Wear thick, soft socks and avoid wearing slippery stockings, mended stockings, or stockings with seams.

·        Wear shoes that fit your feet well and allow your toes to move.  Break in new shoes gradually, wearing them for only an hour at a time at first.  After years of neuropathy, as reflexes are lost, the feet are likely to become wider and flatter.  If you have difficulty finding shoes that fit, ask your doctor to refer you to a specialist, called a podiatrist, who can provide you with corrective shoes or inserts.

·        Examine your shoes before putting them on to make sure they have no tears, sharp edges, or objects in them that might injure your feet.

·        Never go barefoot, especially on the beach, hot sand, or rocks.

·        Cut your toenails straight across, but be careful not to leave any sharp corners that could cut the next toe.

·        Use an emery board or pumice stone to file away dead skin, but do not remove calluses, which act as protective padding.  Do not try to cut off any growths yourself, and avoid using harsh chemicals such as wart remover on your feet.

·        Test the water temperature with your elbow before stepping in a bath.

·        If your feet are cold at night, wear socks. (Do not use heating pads or hot water bottles.)

·        Avoid sitting with your legs crossed.  Crossing your legs can reduce the flow of blood to the feet.

·        Ask your doctor to check your feet at every visit, and call your doctor if you notice that a sore is not healing well.

·        If you are not able to take care of your own feet, ask your doctor to recommend a podiatrist (specialist in the care and treatment of feet) who can help.

Are There Any Experimental Treatments for Diabetic Neuropathy?

Several new drugs under study may eventually prevent or reverse diabetic neuropathy.  However, extensive testing is required by the U.S. Food and Drug Administration to establish the safety and efficacy of drugs before they are approved for widespread use.

Researchers are exploring treatment with a compound called myoinositol.  Early findings have shown that nerves in diabetic animals and humans have less than normal amounts of this substance.  Myoinositol supplements increase the levels of this substance in tissues of diabetic animals, but research is still needed to show any concrete lasting benefits from this treatment.

Another area of research concerns the drug aminoguanidine.  In animals, this drug blocks cross-linking of proteins that occurs more quickly than normal in tissues exposed to high levels of glucose.  Early clinical tests are under way to determine the effects of aminoguanidine in humans.

Another approach is the use of aldose reductase inhibitors (ARIs).  ARIs are a class of drugs that block the formation of the sugar alcohol sorbitol, which is thought to damage nerves.  Scientists hoped these drugs would prevent and might even repair nerve damage. 

Supplements such as Alpha Lipoic Acid, Evening Primrose Oil, L-Carnitine have also been studied.  Additionally, various nerve growth factors have been tested in clinical trials.

So far, with the exception of the DCCT which showed good glucose control decreases the progression of neuropathy, all other clinical trials have failed to show significant results in treating the underlying neuropathy although many drugs have been useful for treating the pain of neuropathy.

Some General Hints

·              Ask your doctor to suggest an exercise routine that is right for you.  Many people who exercise regularly find the pain of neuropathy less severe.  Aside from helping you reach and maintain a healthy weight, exercise also improves the body's use of insulin, helps improve   circulation, and strengthens muscles.  Check with your doctor before starting exercise that can be hard on your feet, such as running or aerobics.

·              If you smoke, try to stop because smoking makes circulatory problems worse and increases the risk of neuropathy and heart disease.

·              Reduce the amount of alcohol you drink.  Recent research has indicated that as few as four drinks per week can worsen neuropathy.

·              Take special care of your feet.

Clark, C.M., & Lee, D.A., Prevention and treatment of the complications of diabetes mellitus, The New England Journal of Medicine, May 4, 1995, pp. 1210-1218.

Overview

This letter hopefully will clearly explain the rationale and use of the Tacticon for measuring peripheral neuropathy. Having conducted research in diabetic neuropathy for 20 years, I became acutely aware of the lack of instruments available to the primary care practitioner to accurately measure neuropathy. Most physicians are still using the crude devices we were trained on in medical school such as the tuning fork, pin, cotton wisp, hot/cold test tubes, reflexes, etc. While these may be adequate for screening purposes, the neuropathy must be clearly demonstrable before these crude devices can detect subclinical or minimally clinical neuropathy. In comparison, the devices and tests I have utilized in clinical research studies were very sophisticated and very capable of detecting and quantifying neuropathy.  However, these devices often cost upwards of $50,000 and often require special training such as electrophysiology. Hence, for many years there was a void in not having a device that could be used for both screening (to pick up undetected neuropathies) and quantification (to be able to make early treatment decisions before severe complications have set in) that was practical in the primary care setting.  In an attempt to address this void, various simple, screening devices have been employed such as the monofilament for touch pressure. These devices all suffer from the same limitation in that they do not quantify the degree of neuropathy and don’t detect sub-clinical neuropathy. Often, the results of these tests give false positive and false negative answers.

In an attempt to address this lack of an intermediate device, I invented the Tacticon some years ago as an inexpensive device that can be utilized to accurately quantify the degree of neuropathy using a standardized, two alternative, forced choice algorithm which is accepted by the FDA.  Two clinical studies have been published on the Tacticon, with both showing close correlations to the sophisticated tests and the ability to detect subclinical neuropathy. Based on this data, the FDA approved the sale of this device for detection and quantification of peripheral neuropathy.  Currently, it is the only known device in this price range that can provide this degree of measurement in the hands of primary care physicians and nurses.  If utilized extensively, many costly foot ulcers, amputations, etc can be avoided since early measures can be taken to avoid foot trauma once subclinical neuropathy is detected.

I hope this explanation is adequate but if not, please do not hesitate to call me at. Appended below is an overview of the rationale and history you might find useful.

Sincerely yours,

Charles Laudadio, MD, MBA

Conventional Treatments for Diabetic Foot Neruopathy:  From a survey of physicians:

Burning pain in the feet in diabetes occurs for a variety of reasons and the underlying cause needs to be sought if treatment is to be appropriate.

1. If the pain is between the first and the second toes in the intermetatarsal space and there is tenderness over a point, then the diagnosis is neuroma and this requires a local injection of a steroid plus local anesthetic. If this does not work, then excision should be performed. The diagnosis can be confirmed with magnetic resonance imaging (MRI) of the foot.

2. If the burning pain is on the sole of the foot and there is tenderness of the sole, then the diagnosis is likely to be a fasciitis and the treatment is nonsteroidal anti-inflammatory agents and, if necessary, steroid injection into the foot pad.

3. If the pain is on the inside or outside of the foot it is likely due to entrapment of the medial or lateral plantar nerves and should be treated with diuretics, nocturnal splints, and steroid injections. If this does not work, surgery may be required to un-entrap the nerves.

4. If the diabetes has recently been exacerbated and insulin has just been started, then this is insulin neuritis, which will respond to mild analgesics and is self-limiting.

5. If the foot is hot and red and there is increased blood flow, the diagnosis is acute Charcot neuroarthropathy and the treatment is intravenous infusion of a bisphosphonate.

6. If the pain is generalized and does not conform to any of the above, it is the small-fiber pain syndrome of diabetes. The first step is to try clonidine 0.1 mg given at night and then building slowly over several weeks to a maximum of 0.5 mg. If this does not work, try topical capsaicin: 1-4 teaspoons of Cayenne pepper in a 4-ounce jar of cold cream applied daily with plastic gloves (and the gloves disposed of) and preferably covering the area with plastic wrap (ie, Saran Wrap). If this fails, try gabapentin, in increasing doses from 300-1800 mg per day, or topiramate 25 mg, increasing to 400 mg per day. Tramadol 50-100 mg given every 4-6 hours may be used to rescue the patient from breakthrough pain.

One must not neglect foot hygiene under any circumstances. There are some interesting new studies using monochromatic infrared light emission (MIRE) and magnets, which requires a separate discussion.

OVERVIEW

A diagnosis of diabetic peripheral neuropathy is dependent on the criteria used to define neuropathy as well as the methodologies and techniques to quantify its severity.  There are no standardized agreements on grading, scoring or assessment techniques. However, two meetings of the American Diabetes Consensus Panels on peripheral neuropathy in diabetes (1988 and 1992), adopted a definition of diabetic neuropathy as  "a demonstrable disorder, either clinically evident or subclinical, that occurs in the setting of diabetes mellitus without other causes for peripheral neuropathy. The neuropathic disorder includes manifestations in the somatic and/or autonomic parts of the peripheral nervous system."  To fulfill this definition, a complete family and personal history, a comprehensive physical and neurological examination, quantitative clinical testing and laboratory evaluations are needed to rule out non-diabetic nerve disease.  The consensus panel’s review of the validity, reproducibility and concordance of the available methodologies for in assessing diabetic peripheral neuropathy identified the following evaluations are the most useful and practical: signs and symptoms; electrophysiology, autonomic nervous system testing and quantitative sensory testing (QST). They recommended that to fully classify neuropathy, at least one measure from each of the above categories should be obtained.

The peripheral neuropathies are generally progressive and irreversible. In the advanced stages they often cause severe pain, ulcerations, amputations and infections, which can be difficult to treat. Therefore, early detection is of paramount importance since the earliest stages respond best to preventive measures and treatment. Early detection is difficult since the current diagnostic methods are either insensitive or too sophisticated for primary care applications. The neurological examination can detect only gross clinical neuropathy and not sub-clinical neuropathy.  Thus, unless clear clinical evidence of peripheral neuropathy is present, it is rarely diagnosed

Consider the analogy to blood pressure screening.  Before sphygmomanometers were used to screen for high blood pressure, hypertension was not detected until patients developed strokes or other clinical manifestations of hypertension.  Once an association was established between hypertension and these complications and a simple device (the sphygmomanometer) became available to the primary care provider to easily measure blood pressure, screening of patients became a commonplace event. During screening, if hypertension was discovered, patient management of salt intake, weight loss, etc. was instituted.  When medications became available to treat hypertension, the sphygmomanometer allowed the provider to monitor the effects of the drugs and monitor the patient’s response to treatment to allow him/her to titrate the doses, add other drugs or change the medication if no response was seen.

With peripheral neuropathy, we are at a crossroad reminiscent of hypertension many years ago. If sphygmomanometers were not available to measure blood pressure in the office setting, providers would be required to send their patients to cardiologists (who would have sophisticated, expensive equipment to measure blood pressure) to determine if hypertension was present.  If detected, the primary care provider could institute therapy but could not monitor the treatment effects or progression.  This analogy applies to peripheral neuropathy today!  Unless there is clear clinical evidence of peripheral neuropathy, the primary care provider cannot easily or cost effectively assess neuropathy, requiring neurology consults whenever neuropathy was suspected or in patients who had a high risk of developing neuropathy (e.g. diabetics).  Once neuropathy is quantified by the neurologist, the primary care provider cannot easily monitor the patient for subtle changes in severity so the success or failure of patient management cannot be monitored.  If specific treatments for neuropathy became available, there are no cost effective and sensitive ways to monitor patients nor follow their response to treatment.  Thus, the Tacticon^® is to peripheral neuropathy what the sphygmomanometer is the hypertension.

Comprehensive testing for neuropathy can assess decreased sensation (i.e. increased thresholds) to vibration, proprioception, light touch, circumference discrimination, temperature perception and pain thresholds.  In the past, diabetic neuropathy have been assessed principally on the basis of neuropathic signs and symptoms, including sensorimotor and reflex measures. These clinical measures generally lack precision and reliability, leaving the subtle forms of dysfunction undetected. Often there are wide discrepancies in the findings from one examiner to another or in repeat assessments of a single individual.

Current sensory testing methods often fail to discriminate between stimulus intensity and perception. All depend on the qualitative assessment of both physician and patient and testing is not well standardized. For example, one common test to assess vibration perception employs an oscillating tuning fork placed over a bony prominence. Results are dependent on the force of the initial strike, the pressure applied to the tested area, the examiner's estimate of decay time, and the patient's perception that the stimulus is no longer present. Negative symptoms, such as numbness, are particularly problematic; they are often insidious in onset, and patients with even moderate to severe involvement may remain unaware of the gradual sensory change.

The inability to quantify sensory impairment in an objective fashion makes repeat assessments of individuals or testing by different clinicians unpredictable.  Diabetic neuropathy involves both small and large nerve fibers, however clinical assessment of small-fiber function is limited to examination with a sharp pin and a cold (or hot) object.  Electrophysiology (EMG) measures large-fiber function, and although standardized and objective, cannot fully assess small fiber diabetic neuropathy. 

To properly and sensitively assess the severity, type and change in peripheral neuropathy, various testing methodologies must be employed to cover the scope of the pathologies. These methodologies include electrophysiology, quantitative sensory testing, neurological examination, assessment of patient symptoms and autonomic function testing.

Quantitative sensory testing (QST) is a testing procedure designed to facilitate the early diagnosis and accurate assessment of diabetic neuropathy. Current evidence indicates the stabilization or reversal of neuropathy may be possible only in its early stages suggesting that effective pharmacologic treatments will have to be applied during the early stages. The ability to detect subclinical neuropathy and to assess a patient’s response to treatment depends on the availability of tests that are objective, quantitative, quick, easy to obtain, reliable, valid, and inexpensive.  Quantitative sensory testing fulfills many of these requirements by utilizing instruments that control and deliver specific stimuli at specified intensities in order to determine a patient’s sensory threshold, defined as the minimal stimulus energy detectable more than 50% of the time.  QST is non-invasive, requires approximately 10 minutes per testing session, and can be administered by nonprofessional personnel after a brief training period. The hallmark of quantitative sensory testing is its ability to administer stimuli precisely.

Quantitative sensory testing is not new.  Hearing is no longer assessed by clinical impression, but by an audiogram that precisely quantifies the threshold of hearing in decibels, at specific frequencies. Assessment of somatosensory function, in the past, had been less quantitative, due primarily to the lack of devices capable of delivering stimuli of appropriate characteristics and intensities. The relatively recent development of somatosensory QST methods and instruments has contributed significantly to the assessment of peripheral nerve function. The past decade has seen many new devices become available, many that are driven by computer and require minimal operator interaction.  These devices are being used to assess vibration and thermal thresholds in research studies and special clinics.  Unfortunately, the cost of these devices usually precludes their use in the office setting.  However, the data from these studies confirms the value of quantitative sensory testing as a measure of diabetic neuropathy since elevation of great toe thresholds may be the earliest reliable sign of the onset of diabetic neuropathy.

For information on the study and to view the Protocols For The Quantitative Sensory Testing Study To Detect Sub-Clinical Neuropathy

Go to www.diabetesincontrol.com/study11.htm

ABSTRACTS on the TACTICON®

1.      The Tactile Circumference Discriminator  (Tacticon^®): A New, Simple Portable Instrument for Identifying Diabetic Patients at Risk of Foot Ulceration

L Vileikyte, G Hutchings, AJM Boulton

Department of Medicine, Manchester Royal Infirmary, Manchester, UK.

The TCD (Tacticon^®) is a new, inexpensive quantitative sensory testing device, consisting of a hand-held disc with eight  protruding rods of increasing circumference, that tests large-fibre nerve function (2 point discrimination).  The ability of the TCD to identify risk of ulceration and neuropathy was tested on the great toe in 133 diabetic patients (mean age 57, range 22-89 years), and compared with vibration perception threshold (VPT) measurement using a neurothesiometer and pressure perception thresholds (PPT) using Semmes-Weinstein monofilaments.  Scores in TCD testing vary from 1 to >7, according to ability to differentiate between rod circumferences, normal values <3 (under 50 years), <4 (>50 years).  The TCD was easy to use and there was a highly significant agreement in its ability to identify neuropathy patients compared with both PPT and VPT (p<0.0001). Similarly TCD agreed with VPT and PPT when identifying patients at risk of ulceration in 91.1% and 96.5% of cases respectively.  In the identification of the 37 foot ulcer patients, TCD was highly sensitive (100%), but less specific (71%) than VPT (97%; 76%) and PPT (100%; 82%).  The TCD is therefore a simple and reliable new technique for population screening in neuropathy and foot ulcer identification, and is the cheapest of the three devices.

2.    The Tactile Circumference Tester (Tacticon™): A New Device for the In-Office Assessment of Sensory Loss in Diabetes

Arezzo,J., Laudadio,C., Litwak,M., and Shamoon,H., USA

The accurate measurement of distal sensory function in persons with diabetes is increasingly important as efficacious treatments for neuropathy become available.  We examined a new, hand-held, mechanical device that allows rapid delivery of tactile stimuli which vary in circumference from 12.5 to 40.0 mm.  Difference thres­holds can be evaluated using a two alternative forced ­choice procedure (5 min/site). Twenty-eight control subjects (age 51.4±9.2 yrs) and 25 subjects with dia­betes (age 54.6 ± 6.4 yrs) were tested.  In the diabetic population, mean HbA_lC was 9.1 % (normal < 6.2%); 14 subjects had IDDM.  For controls, thresholds were 3.9±2.2 and 6.9±3.7 mm at the index finger and great toe, respectively; equivalent values for subjects with diabetes were 8.4 ± 3.2 and 18.4 ± 5.2 mm.  All differences were significant (p<0.01). Thresholds were significantly elevated in comparison to age-matched controls even for the diabetic subjects that reported no neuropathic symptoms (N=15).  Thresholds were highly correlated with age in both normal and diabetic subjects (r=0.4 and 0.5) and the repeat measure coefficient of variation (N=10) was <10%.  The ability to discrim­inate circumference is a variant of the well documented two-point discrimination test. The Tactile Circum­ference Tester (Tacticon™) allows circumference to be quantified, varied along a continuum and presented uniformly.  Our findings support the sensitivity and reliability of this inexpensive device for assessing neuropathy in diabetes.

3. A Cross-Sectional Study Comparing Two Quantitative Sensory Testing Devices in Individuals With Diabetes.  Raelene E. Maser, PHD, Charles Laudadio, MD,  M. James Lenhard, MD,  G. Stephen DeCherney, MD.  Diabetes Care, Vol. 20, No. 2, pp 179-181, February 1997.  Medical Center of Delaware, Medical Research Institute, Newark, DE

QST has been recommended as a modality to be used in the full assessment of diabetic neuropathy. We have evaluated a new portable,  palm size QST device (Tacticon^®) that evaluates large sensory fibers.  The results of testing with this device were compared with vibratory thresholds (VT[Vibratron II]). Sensory thresholds for the great toe were determined for both modalities using a two alternative forced choice procedure.  Utilizing the Tacticon^™, thresholds were determined as the ability to discriminate between the smallest circumference of seven metal rods (12.5- 40 mm) compared to a reference rod (12.5 mm). One Hundred and fifty diabetic subjects aged 52±17 yrs (mean±SD, range 18-83 yrs) with a duration of 12±9 yrs of diabetes and a BMI of 30±7 kg/m² were evaluated.  There were 73 men and 77 women with 67% of the cohort having NIDDM. Subjects were divided into three groups based on increasing circumference discrimination thresholds (CDT). Statistically significant differences in VT were found when comparing all groups (p<0.001)

Age Group	Patients per Group	Rod#	Neuropathy Classification	*CDT (mm)	VT (vibration units)
50	37	1,2,3	Normal	2.5 to 7.5	2.0±1.0
50	21	4,5	Mild	12.5 to 17.5	3.9±1.8
50	4	6,7	Moderate	22.5 to 27.5	6.4±2.5
50	5	>7	Severe	32.5	13.1±3.8
>50	24	1-4	Normal	2.5 to 12.5	3.6±1.2
>50	15	5-6	Mild	17.5 to 22.5	7.2±2.9
>50	9	7	Moderate	27.5	9.1±3.3
>50	35	>7	Severe	32.5	11.9±4.3

*CDT=Threshold Rod (in mm) - Reference Rod-0 as 12.5 mm

CDTs were elevated in 100% of diabetic patients >65 yrs old but only in 62% of those <45 yrs old. Our data suggests the Tacticon^® offers an inexpensive, sensitive method of screening for neuropathy.

www.diabetesincontrol.com/study11.htm

Email: publisher@diabetesincontrol.com