(A) Distal symmetric sensorimotor polyneuropathy: This is the most common type of diabetic peripheral neuropathy. The symptoms start from the distal extremity and gradually develop proximally, with a glove-sock-like distribution range, usually starting from the lower extremity. Sensory impairment is predominant, with varying degrees of autonomic symptoms, while motor impairment is relatively mild. The onset of the disease is mostly insidious. The manifestation of sensory symptoms is related to the size of the involved nerve fibers. In the case of small fibers, pain and sensory abnormalities are the main symptoms. Pain can be a variety of pain manifestations such as dull, burning, stabbing, and cutting pains, mostly increasing in the evening. Abnormal sensation can be numbness, coldness, ants, insects, heat, burning, electric shock, and other sensations. Deep sensory (joint position and vibration) disturbances are generally mild. There can also be hyperalgesia or absence of temperature and pain sensation. As symptoms worsen, various accidental injuries to the distal part of the limb can occur without any knowledge, such as burns, hot water burns, ulcers caused by foot trauma, etc. Autonomic neuropathy caused by the foot does not sweat, resulting in dry and cracked skin, which is more likely to promote the occurrence of ulcers. Secondary infection of foot ulcers with arterial thrombosis can cause necrosis and gangrene, leading to eventual amputation. If coarse fibers are involved, joint position and vibration sensation are mainly affected. Symptoms of unsteadiness in gait and standing, more pronounced with the eyes closed, are known as sensory ataxia. Patients often complain of a sensation of stepping on cotton or a strange feeling on the floor. The unsteadiness of movement may lead to falls, trauma or even fractures. Clinically, damage to small fibers is more common, but the most common case is a mixed type of disease in which both small and large fibers are involved. Motor deficits such as distal weakness and small muscle atrophy of the hands and feet are usually seen in the later stages of the disease. (B) Autonomic neuropathy: Autonomic neuropathy tends to rarely occur alone and is often accompanied by somatic neuropathy. Conversely, the incidence of some degree of autonomic dysfunction can be found in up to 40% of diabetic cases with somatic neuropathy by functional examination. However, once clinical symptoms of autonomic dysfunction appear, the prognosis may be poor. 1. Cardiovascular system (1) Upright hypotension: When a patient rises from a recumbent position, if the systolic blood pressure in the standing position falls by more than 30 mmHg compared with that in the recumbent position, it is called upright hypotension. (2) Tachycardia at rest: The heart rate at rest is 90 to 100 beats/min, some up to 130 beats/min. (3) Painless myocardial infarction: It is the most serious manifestation of cardiac autonomic dysfunction. (4) Sudden death: In diabetic patients with severe autonomic neuropathy, respiratory and cardiac arrests have occurred. 2, gastrointestinal system: diabetic gastroparesis can be manifested as nausea, abdominal distension and pain after eating, early satiety, vomiting, etc.. Most diabetic patients have constipation, but there are a few patients with diarrhea, or alternating diarrhea and constipation. 3, genitourinary system and diabetic cystopathy: bladder dysfunction can be seen in 37-50% of diabetic patients. Bladder symptoms associated with autonomic neuropathy include dyspareunia, decreased urinary flow,, high residual urine, incomplete urination, urinary retention, sometimes urinary incontinence, and easily complicated by urinary tract infections. Reproductive system manifests as decreased libido and impotence in men. The reported incidence is 30-75%. Impotence may be the earliest symptom of diabetic autonomic neuropathy. 4. Sweating abnormalities: Sweat gland innervation nerve dysfunction is a common symptom of diabetic autonomic neuropathy. The main manifestation is less sweating at the ends of the extremities, but it is often accompanied by excessive sweating in the trunk area. (iii) Acute painful neuropathy This type is rare and mainly occurs in diabetic patients with poorly controlled disease. The acute onset of severe pain and nociceptive hypersensitivity is most pronounced in the distal lower extremities and may spread to the entire lower extremity, trunk or hands. It is often accompanied by muscle weakness, atrophy, weight loss and depression, and some patients present with neuropathic hyperemesis. This type has a better effect on insulin therapy, but the recovery time is often longer. (iv) Cerebral neuropathy Among the diabetic single cerebral neuropathy, the most common one is oculogyric nerve palsy. It starts as diplopia and progresses to complete ocular muscle paralysis within a few days, with ptosis and dilated pupils. Diabetic ophthalmic nerve palsy usually recovers spontaneously within 6-12 weeks, but recurrence or bilateral lesions can occur.