MACULAR EDEMA, AND OTHER OCULAR COMPLICATIONS
Annual dilated funduscopic examinations are recommended; follow-up
evaluation and treatment for abnormalities by ophthalmologists with specific
expertise in fluorescein angiography and laser therapy can reduce
visual loss. Cataract extraction in the setting of diabetic retinopathy
can be associated with visual loss related to macular edema and requires
special attention to avoid poor outcomes. Glaucoma seems to be more
prevalent in people with diabetes. Expert eye care is essential for optimal
outcomes in people with diabetes.
Diabetic retinopathy refers to progressive pathologic alterations
in the retinal microvasculature, leading to areas of retinal nonperfusion,
increased vascular permeability, and the pathologic proliferation of retinal
vessels. In the United States, diabetes is the leading cause of blindness
in persons aged 20 to 74 years. Retinopathy in patients with poorly
controlled type 1 diabetes occurs in about 25% of patients 5 years after
diagnosis, in 60% at 10 years, and in more than 95% at 15 years. Blindness
occurs 25 times more frequently in diabetic patients than in control subjects
and is seen most often after the disease has been present for at least 15
years, in the setting of advanced retinopathy. Approximately 10 to 15% of
type 1 diabetic patients will become legally blind (visual acuity of 20/200
or worse in the better eye). In type 2 diabetes, though the incidence of
blindness is lower, higher disease prevalence results in an even larger number
of patients affected with severe visual loss.
Mild nonproliferative diabetic retinopathy (mild
NPDR) is the earliest pathologic changes associated with retinopathy
In type 1 patients, these changes generally begin 3 to 5 years after
diagnosis. The first signs of mild NPDR are
microaneurysms, which arise most often
in areas of capillary occlusion. Subsequently, increasing vascular permeability
leads to retinal blot hemorrhages (round, with blurred
edges) and "hard" exudates (sharply defined and yellow). Infarctions
of the nerve fiber layer, known as "soft" exudates
or "cotton-wool spots," appear as white or gray, rounded swellings.
At this early stage of retinopathy, visual acuity is generally unaffected,
and the risk of progression to high-risk proliferative diabetic retinopathy
(PDR) is about 15% at 5 years.
Moderate NPDR is characterized by
intraretinal microvascular abnormalities,
including venous caliber changes, beading, and increased capillary dilatation
and permeability. Later changes, termed severe or very severe NPDR,
include progressive retinal capillary loss and ischemia, with further
development of extensive hemorrhages, exudates,
and microaneurysms. At 5 years, moderate and severe NPDR are
associated with a 30% and 60% risk of progression to high-risk PDR, respectively.
Proliferative diabetic retinopathy (PDR)
involves neovascularization, the growth of fine tufts of
new blood vessels and fibrous tissue from the inner retinal surface or the
optic head. Early proliferative changes are confined to the retina, but later
invasion of the vitreous body constitutes high-risk PDR; during this end
stage, fibrosis and contracture of the neovasculature
results in retinal detachment and hemorrhage, the most important
determinants of blindness. Occasionally, new vessels can invade the iris
and anterior chamber, leading to sight-threatening
Clinically significant macular edema (CSME)
results from vascular leakage at the macula and can occur either
with or without the stages of retinopathy described earlier. CSME is suggested
by hard macular exudates on fundoscopic examination and can be confirmed
with slit lamp biomicroscopy. In general, maculopathy is more common in type
2 patients, in whom it is an important contributor to the loss of visual
acuity. As will be discussed, the treatment of CSME runs parallel to the
treatment of other forms of diabetic retinopathy.
Duration of diabetes is closely associated with the onset and severity of
diabetic retinopathy. Diabetic retinopathy is rare in prepubescent patients
with type 1 diabetes, but nearly all patients with type 1 diabetes and more
than 60% of patients with type 2 diabetes develop some degree of retinopathy
after 20 years. In patients with type 2 diabetes, approximately 20% have
retinopathy at the time of diabetes diagnosis and most have some degree of
retinopathy over subsequent decades.
Diabetic retinopathy is the most frequent cause of new-onset blindness among
American adults aged 20 to 74 years.
Lack of glycemic control is another significant risk factor for the onset
and progression of diabetic retinopathy. The DCCT demonstrated a clear
relationship between hyperglycemia and diabetic microvascular complications,
including retinopathy in 1441 patients with type 1 diabetes.
In addition to the importance of intensive glycemic control in reducing the
onset and progression of diabetic retinopathy as discussed earlier, it is
critical for optimal ocular health of diabetic patients that several other
systemic considerations (as hypertension, proteinuria, hyperlipidemia) be
Elevated BP exacerbates the development and progression of diabetic
Associations between renal and retinal angiopathy are numerous. Proteinuria
or microalbuminuria is associated with retinopathy. The presence
and severity of diabetic retinopathy are indicators of the risk of gross
proteinuria, and, conversely, proteinuria predicts PDR.
The effects of serum lipids on retinopathy and macular edema are less
Smoking is a certain risk factor for CVD, progression of albuminuria
to proteinuria, and nephropathy in both type 1 and 2 diabetic patients. However,
the effects of smoking on diabetic retinopathy are unclear.
At present, medical management of diabetic retinopathy
is aimed at controlling risk factors for progression as tight control of
hyperglycemia, hypertension, hyperlipidemia, nephropathy, careful follow-up
during pregnancy, and a good regular eye exam and follow up by an
Diabetic nephropathy is the leading cause of end-stage renal disease
requiring dialysis or transplantation. Early kidney disease is detectable
as an increase in the microalbumin to creatinine ratio on a spot urine sample
(>30 µg albumin per mg creatinine). This screening procedure should
be performed annually. Patients exhibiting microalbuminuria should be treated
with ACE inhibitors or ARBs, and their blood pressure treated to less than
130/80 mm Hg. If the creatinine is increased above normal or if the urinary
sediment is active, consultation with a nephrologist or other provider with
special expertise in the evaluation of kidney disease may be useful to direct
overall treatment and to exclude other causes of kidney disease.
Diabetic nephropathy is clinically defined by persistent proteinuria
greater than 500 mg/24 hours in a person with diabetic retinopathy without
other renal disease. Listed as the chief cause of end-stage renal disease
(ESRD) in North America, Japan, Korea, and most industrialized European nations,
diabetic nephropathy in 1998 accounted for 44.5% of incident ESRD patients
funded by Medicare. Typically, diabetic ESRD patients have serious
co-morbid conditions, especially heart, eye, and peripheral vascular diseases.
It is not surprising, therefore, that caring for afflicted individuals imposes
a major financial burden on family members and governments.
Both type 1 and type 2 diabetes cause renal disease. Compared to type 1,
a slightly smaller and imperfectly defined proportion of type 2 patients
progress to ESRD, but they represent more than 90% of those receiving renal
replacement therapy with the diagnosis of diabetes.
Listed as the chief cause of end-stage renal disease (ESRD) in North America,
Japan, Korea, and most industrialized European nations, diabetic nephropathy
in 1998 accounted for 44.5% of incident ESRD patients funded by Medicare
. Typically, diabetic ESRD patients have serious co-morbid conditions,
especially heart, eye, and peripheral vascular diseases.
Both type 1 and type 2 diabetes cause renal disease. Compared to type 1,
a slightly smaller and imperfectly defined proportion of type 2 patients
progress to ESRD, but they represent more than 90% of those receiving renal
replacement therapy with the diagnosis of diabetes.
Kidney injury in diabetes is indistinguishable by diabetes type and affects
glomeruli, arterioles, tubules, and interstitium.   Glomerular
lesions include diffuse and nodular forms of intracapillary glomerulosclerosis.
NEPHROPATHY IN TYPE 1 DIABETES
The natural history of diabetic nephropathy has been extensively studied
in type 1 diabetes because it is usually possible to specify the exact time
of onset. As first described by Mogensen, there are five distinct stages.
The course of diabetic nephropathy can be followed by two main variables:
proteinuria and GFR.
Stage 1: Glomerular Hyperfiltration and Renal Enlargement
At onset of type 1 diabetes, approximately one third of individuals have
an elevated GFR that is 20% to 40% higher than that of age-matched normal
Stage 2: Early Glomerular Lesions or Silent Stage with Normal Albumin
Those structural changes appear 18 to 36 months and may become prominent
after 3.5 to 5 years after onset of type 1 diabetes..
Stage 3: Incipient Diabetic Nephropathy or Microalbuminuric Stage
The third stage, also called incipient diabetic nephropathy, is characterized
by persistent and usually increasing microalbuminuria. Hypertension
may also be a feature of the microalbuminuric stage. Hyperfiltration and
renal enlargement persist, though to a lesser degree. Microalbuminuria, defined
as urinary AER greater than 30 mg/24 hours or 20 µg/minute and less
than 300 mg/24 hours or 200 µg/minute, represents the first laboratory
evidence of diabetic renal disease.
The prevalence of microalbuminuria varies from 25% to 40% in individuals
with type 1 diabetes for 5 to 15 years.
Persistent microalbuminuria rarely occurs during the first 5 years of type
1 diabetes or before puberty.
Stage 4: Clinical or Overt Diabetic Nephropathy: Proteinuria and Falling
Glomerular Filtration Rate
Albuminuria greater than 300 mg/24 hours, relentless decline of renal function,
and hypertension define the fourth stage of diabetic nephropathy. This
stage, though variable, usually occurs 15 to 20 years after the onset
of type 1 diabetes and after 5 or more years of diagnosed type 2
diabetes. The amount of urinary protein can be as little as 500 mg, but
it can reach massive proportions, such as 20 to 40 g/24 hours. Continuing
urinary protein loss of this magnitude is associated with increased glomerular
pore size. There is a high mortality rate associated with proteinuria. Median
survival is 10 years from the onset of proteinuria.
Diagnoses other than diabetic nephropathy should be pursued whenever a nephrotic
syndrome develops in a patient with short-term type 1 diabetes or
in the absence of retinopathy.
In subjects with type 1 diabetes, the prevalence of arterial hypertension
ranges from 65% to 79% when macroalbuminuria is present. Hypertension
intensifies the rate of progression of established diabetic renal disease.
Stage 5: End-Stage Renal Disease
After 20 to 30 years of type 1 diabetes, about 30% to 40% of patients
progress to ESRD. Recently, the interval between the onset of persistent
proteinuria and the final stage of diabetic nephropathy has been lengthened
by early and intensive treatment of hypertension and enhanced metabolic control
NEPHROPATHY IN TYPE 2 DIABETES
Although renal structural changes and severity of target organ damage are
similar in both types of diabetes, delayed diagnosis has complicated the
construction of the natural history of diabetic renal disease in type 2 diabetes.
14-24% of newly diagnosed patients with type 2 diabetes have microalbuminuria,
which is associated with hyperglycemia, elevated BP, smoking, and
Microalbuminuria in type 2 diabetes is partially reversed by reduction of
hyperglycemia and high BP.
Microalbuminuria raised the overall odds ratio for death to 2.4 and
cardiovascular mortality to 2.0 over those without microalbuminuria.
Hypertension is highly characteristic of renal disease in type 2 diabetes,
whether the individuals are normoalbuminuric, microalbuminuric, or
Treatment of Diabetic Nephropathy:
Strict glycemic control is of the utmost importance.
Dietary protein restriction (i.e., 0.8 g/kg of body weight)
ACE inhibitors and angiotensin II receptor blockers have consistently
shown a delay in the progression of both proteinuria and declining GFR
Good blood pressure control
Good lipid control
Hemodialysis or Peritoneal dialysis in ESRD (End Stage Renal Disease)
Early treatment of diabetic neuropathy should include
tight glycemic control.
Diabetic neuropathy can be disabling as a consequence of autonomic
dysfunction or discomfort. Symptomatic therapy of these various syndromes
is beyond the scope of this chapter because there is no single agent that
routinely works in even the most affected patients. The insensate foot
is the strongest predictor of the risk for foot ulceration and amputation.
Annual foot examinations focusing on skin integrity, structural
abnormalities, adequacy of perfusion and neurologic function is essential.
The Semmes-Weinstein 5.07- or 10-g filament is a particularly essential
tool to use to evaluate sensory function, because most patients with insensate
feet are unaware of their lack of sensation. People who cannot consistently
feel the touch of the 10-g filament are at high risk of ulceration and should
enter a comprehensive program of foot care, generally led by a
podiatrist or other foot care specialist, including the use of
emollients, special shoes, routine nail care, and careful daily self-examinations
looking for early lesions.
Diabetic neuropathy (DN) is a common and troublesome complication
of diabetes mellitus, leading to great morbidity and mortality and resulting
in a huge economic burden for care of the patient with diabetes mellitus.
It is the most common form of neuropathy in the developed countries of the
world, accounts for more hospitalizations than all the other diabetic
complications combined, and is responsible for 50% to 75% of nontraumatic
Diabetic neuropathy is a heterogeneous disorder that encompasses a wide range
of abnormalities affecting proximal and distal peripheral sensory and motor
nerves as well as the autonomic nervous system.
The major morbidity associated with somatic neuropathy is foot
ulceration, the precursor of gangrene and limb loss.
Common types of diabetic neuropathies:
Peripheral or Distal Symmetrical polyneuropathy - is the most
common type. Usually bilateral, the symptoms include numbness,
paresthesias, severe hyperesthesias, and pain. The pain, which may be deep-seated
and severe, is often worse at night. It is occasionally lancinating or lightning
in type, resembling tabes dorsalis (pseudotabes). Fortunately, extreme pain
syndromes are usually self-limited, lasting from a few months to a few
Mononeuropathy , though less common than polyneuropathy, also
may occur. Characteristically, there is a sudden wrist drop, foot drop, or
paralysis of the third, fourth, or sixth cranial nerves. Other single nerves,
including the recurrent laryngeal, have been reported to be involved.
Mononeuropathy is characterized by a high degree of spontaneous reversibility,
usually over a several-week period.
Radiculopathy is a sensory syndrome in which pain occurs over
the distribution of one or more spinal nerves, usually in the chest wall
or abdomen. The severe pain may mimic herpes zoster or an acute surgical
abdomen. Like mononeuropathy, the lesion is usually self-limited.
Autonomic neuropathy may present in a variety of ways. The
gastrointestinal tract is a prime target, and there may be esophageal dysfunction
with difficulty in swallowing, delayed gastric emptying,
constipation, or diarrhea. The latter symptom is often nocturnal.
Incompetence of the internal anal sphincter may mimic diabetic diarrhea.
Orthostatic hypotension and frank syncope may occur.
Bladder dysfunction or paralysis is particularly distressing and often
leads to the necessity of chronic catheter drainage. Impotence and retrograde
ejaculation are additional manifestations in men. Erectile dysfunction
is associated with a failure of nitric oxide generation in the penile
DSPN (Distal Symmetrical Polyneuropathy) increases the risk
of amputation 1.7-fold: 12-fold if there is deformity (itself a
consequence of neuropathy) and 36-fold if there is a history of previous
Once autonomic neuropathy sets in, life can become quite dismal, and the
mortality rate approximates 25% to 50% within 5 to 10 years.
The natural history of diabetic neuropathy separates patients into
two very distinctive entities:
(1) those who progress gradually with increasing duration of diabetes mellitus
(2) those who have a relatively explosive onset and experience remission
almost completely. Sensory and autonomic neuropathies generally progress,
whereas mononeuropathies, radiculopathies, and acute painful neuropathies,
although symptoms are severe, are short-lived and tend to recover.
Progression of DSPN is related to glycemic control in both type 1 and
type 2 diabetes mellitus. The most rapid deterioration of nerve function
occurs soon after the onset of type 1 diabetes mellitus, and within 2 to
3 years there is a slowing of the progress with a shallower slope to the
curve of dysfunction. In contrast, slowing of NCVs in type 2 diabetes mellitus
may be one of the earliest neuropathic abnormalities and is often present
at diagnosis. After diagnosis, slowing of NCV generally progresses
at a steady rate of approximately 1 m/second each year, and the level of
impairment is positively correlated with duration of diabetes mellitus.
In a long-term follow-up study of patients with type 2 diabetes mellitus,
electrophysiologic abnormalities in the lower limb increased from 8% at baseline
to 42% after 10 years, and a decrease in sensory and motor amplitudes, indicating
axonal destruction, was more pronounced than the slowing of the NCVs.
Diabetic neuropathy is not a single entity but a number of different
syndromes, ranging from subclinical to clinical manifestations depending
on the classes of nerve fibers involved.
The onset of neuropathy may be acute, with pain or, insidious, with chronic
pain as well as clinical features of a mixed sensorimotor dysfunction.
According to the San Antonio Convention,
the main groups of neurologic disturbance in diabetes mellitus
include the following:
Subclinical neuropathy, determined by
abnormalities in electrodiagnostic and quantitative sensory testing without
concomitant clinical sign and symptoms.
It is diagnosed on the basis of the following:
Abnormal electrodiagnostic tests with decreased NCV or decreased amplitudes;
Abnormal QST for vibration perception, light touch, thermal warming, and
QAFT revealing diminished heart rate variation with deep breathing, Valsalva
maneuver, and postural testing.
Focal neuropathies, which include
mononeuropathies and entrapment syndromes.
Mononeuropathies occur primarily in the older population,
their onset is generally acute and associated with pain, and their course
is self-limiting, resolving within 6 to 8 weeks. These are due to
vascular obstruction after which adjacent neuronal fascicles take over the
function of those infarcted by the clot.
Treatment is predominantly symptomatic for pain. If there is weakness such
as of the facial muscles, physical therapy and electrical stimulation may
be necessary to prevent the weakness from becoming
Entrapment syndromes that start slowly, progress, and
persist without intervention must be distinguished from mononeuropathies.
Common entrapment sites in diabetes mellitus patients involve median, ulnar,
radial, femoral, and lateral cutaneous nerves of the thigh, peroneal nerves,
and medial and lateral plantar nerves. Entrapment syndromes are found in
one third of patients with diabetes. For example, carpal tunnel syndrome
occurs twice as frequently in people with diabetes mellitus compared with
a normal healthy population. It is important, therefore, to elicit a detailed
history of the distribution of pain and weakness and to perform the equivalent
of Tinel's test at various levels of entrapment. If recognized, the diagnosis
can be confirmed by electrophysiologic studies. There are nonsurgical
and surgical treatment options.
Diffuse clinical neuropathy, which may
proximal motor neuropathy or distal symmetrical neuropathy and
large-fiber symmetrical sensorimotor or
small-fiber neuropathy and
Diffuse (Clinical) Neuropathies
The condition is known by a number of synonyms: proximal neuropathy,
femoral neuropathy, diabetic amyotrophy, and diabetic
Proximal motor neuropathy can be clinically identified based on
recognition of the following common features:
Primarily affects the elderly.
Gradual or abrupt onset.
Begins with pain in the thighs and hips or buttocks, followed by significant
weakness of the proximal muscles of the lower limbs with inability to rise
from the sitting position (positive Gower's maneuver).
Begins unilaterally and spreads bilaterally.
Coexists with DSPN.
Is characterized by spontaneous or percussion-provoked muscle fasciciulation.
Proximal motor neuropathy is now recognized as being secondary to
a variety of causes unrelated to diabetes mellitus but that occur more frequently
in patients with diabetes mellitus than in the general population. The condition
includes patients with chronic inflammatory demyelinating polyneuropathy
(CIDP), monoclonal gammopathy, circulating GM1 antibodies and
antibodies to neuronal cells, and inflammatory vasculitis. It
was formerly thought to resolve spontaneously in 1.5 to 2 years, but now,
if found to be immune-mediated, it can resolve within days of initiation
of immunotherapy. The condition is readily recognizable clinically with
prevailing weakness of the iliopsoas, obturator, and adductor muscles, together
with relative preservation of the gluteus maximus and minimus and hamstrings.
Treatment options include intravenous immunoglobulin for CIDP, plasma exchange
for monoclonal gammopathy of unknown significance, steroids and azathioprine
for vasculitis, and withdrawal from drugs or other agents that may have caused
It is important to divide proximal syndromes into these two subcategories,
because the CIDP variant responds dramatically to intervention, whereas
amyotrophy runs its own course over months to years. Until more evidence
is available, they should be considered separate syndromes.
Distal Symmetrical Polyneuropathy (DSPN)
Distal symmetrical polyneuropathy (DSPN) is the most common and widely
recognized form of diabetic neuropathy. The onset is usually insidious
but occasionally is acute, following stress or initiation of therapy for
diabetes mellitus. DSPN may be either sensory or motor and involve small
nerve fibers, large nerve fibers, or both. Small-fiber dysfunction usually
occurs early and often is present without objective signs or electrophysiologic
evidence of nerve damage. It is manifested by early lower limb symptoms
of pain and hyperalgesia in the lower limbs, followed by a loss of thermal
sensitivity and reduced light touch and pinprick sensation.
Most patients with DSPN, however, have a "mixed" variety of neuropathy, with
both large-fiber and small-fiber damages. In the case of DSPN, a
"glove-and-stocking" distribution of sensory loss is almost universal. Early
in the course of the neuropathic process, multifocal sensory loss also might
be found. In some patients, severe distal muscle weakness can accompany the
sensory loss, resulting in an inability to stand on the toes or heels.
Clinical Manifestations of Small-Fiber Neuropathies
Symptoms prominent. Pain is of the C-fiber type. It is burning and superficial
and associated with allodynia, i.e., interpretation of all stimuli as painful
Late in the condition, hypoalgesia.
Defective warm thermal sensation.
Defective autonomic function with decreased sweating, dry skin, impaired
vasomotion and blood flow, and a cold foot.
Remarkable intactness of reflexes, motor strength.
Loss of cutaneous nerve fibers using PGP 9.5 staining.
Diagnosed clinically by reduced sensitivity to 1.0-g Semmes Weinstein
monofilament and pricking sensation using the Waardenberg wheel or similar
Abnormalities in thresholds for warm thermal perception, neuro-vascular function,
pain, quantitative sudorimetry, and quantitative autonomic function tests.
Risks are foot ulceration and subsequent gangrene.
At present, however, control of hyperglycemia and meticulous foot care are
the mainstays of therapy.
Some of the suggested therapies for painful
Capsaicin or lidocaine topically
Clonidine can be applied topically
Tramadol and Dextromethorphan
Antidepressants as Nortriptyline
Transcutaneous Electrical Nerve Stimulation (TENS)
are rarely of much benefit in the treatment of painful neuropathy, although
they may be of some use on a short-term basis for some of the self-limited
syndromes, such as painful diabetic third nerve palsy. Use of narcotics in
the setting of chronic pain generally is avoided because of the risk of
Recommendatinos for First- and Second-Tiere Agents
for Diabetic Peripheral Neuropathic Pain (DPNP) 2006
First tier Rx:
Duloxetine (Cymbalta), Oxycodone CR,
TCA (Tricyclic Antidepressants)
Second tier Rx:
Venlafaxine ER (Effexor ER)
Bupropion, Citalopram, Metadone, Paroxetine, Phenytoin, Topiramate
RE: Mayo Clinic Proceedings Supplment April
2006, p: S22-23
Acute Painful Neuropathy
In some patients, a predominantly small-fiber neuropathy develops,
manifested by pain and paresthesias early in the course of diabetes mellitus.
It may be associated with the onset of insulin therapy and has been termed
insulin neuritis. By definition, it has been present for less than
6 months. Symptoms often are exacerbated at night and are manifested in the
feet more than the hands. Spontaneous episodes of pain can be severely disabling.
The pain varies in intensity and character. In some patients, the pain has
been variably described as burning, lancinating, stabbing, or sharp. Paresthesias
or episodes of distorted sensation, such as pins and needles, tingling, coldness,
numbness, or burning, often accompany the pain. The lower legs may be exquisitely
tender to touch, with any disturbance of the hair follicles resulting in
excruciating pain. Because pain can be exacerbated by repeated contact of
the lower limbs with foreign objects, even basic daily activities, such as
sitting at a desk, may be disrupted. Pain often occurs at the onset of the
disease and is often worsened by initiation of therapy with insulin or
It may be associated with profound weight loss and severe depression, termed
diabetic neuropathic cachexia. This syndrome occurs predominantly
in male patients and may occur at any time in the course of both type 1 and
type 2 diabetes mellitus.
It is self-limiting and invariably responds to
simple symptomatic treatment.
Chronic Painful Neuropathy
Another variety of painful polyneuropathy is characterized by an onset occurring
later (often years) in the course of diabetes mellitus, in which the pain
persists for longer than 6 months and becomes debilitating. This condition
may result in tolerance to narcotics and analgesics and, finally, to addiction.
It is extremely resistant to all forms of intervention and is most frustrating
to both patient and physician.
Chronic Small-Fiber Neuropathy
Disappearance of these symptoms may not necessarily reflect nerve recovery
but rather nerve death. When patients volunteer the "apparent improvement,"
progression of the neuropathy must be excluded by careful examination. Pain,
however, may persist even with dead nerves. The objective physical features
include loss of warm thermal perception, decreased heat pain, cold pain,
loss of touch pressure perception, and impairment of blood flow. A foot with
these findings is at risk for repeated minor trauma, foot ulceration, infection,
and gangrene. Small-fiber neuropathies have profound effects on quality of
life and mortality.
Large-fiber neuropathies may involve sensory nerves, motor nerves, or both
. These tend to be the neuropathies of signs rather than symptoms.
Large fibers subserve motor function, vibration perception, position sense,
and cold thermal perception.
Characteristic features are wasting of the interosseous muscles of
the hands and feet, giving rise to the hammertoe deformities and pes equinus,
and the loss of hand grip strength and the ability to tie knots and do buttons.
There is a significant impact on activities of daily living.
Objective findings include loss of reflexes, decreased vibration
perception, ataxic gait, and inability to perform a tandem stand or one-legged
stand for longer than 30 seconds. There is no impairment of blood flow, the
feet are often hot, and there is a susceptibility to osteopenia of the feet
and a risk of Charcot's neuroarthropathy.
Clinical Presentation of Large-Fiber Neuropathies
Impaired vibration perception (often the first objective evidence) and position
Depressed tendon reflexes.
A delta type deep-seated gnawing, dull, like a toothache in the bones of
the feet, or even crushing or cramp-like pain.
Sensory ataxia (waddling like a duck).
Wasting of small muscles of feet with hammertoes (intrinsic minus feet and
hands) with weakness of hands and feet.
Shortening of the Achilles tendon with pes equinus.
Increased blood flow (hot foot).
Risk is Charcot's neuroarthropathy.
Management of Large-Fiber
Gait and strength training.
Pain management as detailed in text.
Orthotics should be fitted with proper shoes for the deformities.
Tendon lengthening for Achilles tendon shortening.
Bisphosphonates may be given for osteopenia.
Surgical reconstruction and full-length casting as necessary.
Diabetic autonomic neuropathy may involve any system in the body.
Involvement of the autonomic nervous system can occur as early as the first
year after diagnosis, and major manifestations are cardiovascular,
gastrointestinal, and genitourinary system dysfunction . Reduced exercise
tolerance, edema, paradoxic supine or nocturnal hypertension, and intolerance
to heat due to defective thermoregulation are a consequence of autonomic
Clinical Features of Autonomic Neuropathies
- posture-related dizziness and syncope.
RX: Volume expansion, Supportive Garments, Drug Therapy (9-fluorohydrocortisone,
Metoclopramide, the a2 -antagonist yohimbine, small dose clonidine, a1-adrenergic
Silent myocardial infarction, congestive heart failure, and sudden death
Rx: multiple small feedings, Metoclopramide, Erythromycin given as either
a liquid or a suppository,jejunostomy placement
For Stasis of bowel contents with bacterial overgrowth -Treatment
with broad-spectrum antibiotics is the
mainstay of therapy, including tetracycline or
trimethoprim and sulfamethoxazole.
Metronidazole appears to be the
most effective and should be continued for at least 3 weeks.
Retention of bile may occur and can be highly irritating to the gut.
Chelation of bile salts with cholestyramine 4 g
three times daily mixed with fluid may offer relief of
Diphenoxylate plus atropine may help control diarrhea; toxic
megacolon can occur, however, and extreme care should be used.
In refractory cases, small doses of
octreotide can be helpful in controlling
Sildenafil (Viagra) 50-100 mg
Topically applied glycopyrrolate, an antimuscarinic compound, is effective
treatment in reducing both the severity and frequency of sweating of the
head and neck region while eating food that triggers this reflex.
Disturbed neurovascular flow
Hypoglycemia unawareness, hypoglycemia unresponsiveness