Susan was 75 and could barely walk. She had become uncoordinated and lived in constant fear of falling. Each tiny step required enormous effort. Maintaining even a simple daily routine was becoming impossible. Her primary care doctor had referred her to me, and as she succinctly put it during her first visit to my office, her life was a mess. She said that I was her last resort.
Her symptoms had appeared abruptly, which is uncommon in most chronic neurological diseases. That was an important clue. Three months ago she had developed numbness in her fingers and toes. Within several weeks it had spread to her wrists, then her ankles and feet. This numbness did not come and go, she told me. It was constant. As a result, she was dropping things around the house. This clumsiness affected her legs as well, and she felt very unsteady. Although she wasn’t experiencing vertigo or dizziness, she said that she felt off balance, as if she were drunk. When she walked, the numbness was so profound that she couldn’t feel her feet touching the floor.
Susan said that her speech, vision, swallowing, hearing, and strength were normal. So were her bowel and bladder functions. She did not travel and was not in contact with anyone who was ill. Except for mild high blood pressure and high cholesterol, Susan’s medical history was unremarkable.
A brief general exam revealed no abnormalities. She was vibrant and healthy, and the results from her initial neurological testing were normal. She was alert, oriented, and could follow my hands easily with her eyes. Susan’s strength was typical for women her age, but I found severe deficits in her sensation. She could barely feel a light stroke with my fingers, and she couldn’t feel pinpricks well in her hands and feet. When I used a tuning fork to test how well the nerves in her legs were working, Susan couldn’t feel the fork’s vibration until I reached her knees. When I moved her toes up and down, she couldn’t tell me which direction they were moving in (this ability is called proprioception, or sense of joint position).
I checked her muscle stretch reflexes by tapping her elbows, knees, and ankles with a small hammer. The reflexes were absent at the ankles and knees. Her gait was ataxic: Her feet were planted wider apart than normal, and her walk was unsteady, almost wobbly. When she walked, she had to reach out to the wall to keep from falling.
Something else caught my attention. I asked Susan to close her eyes and stand with her feet together and arms outstretched, as if she were carrying a pizza. When she did, she nearly fell over. Neurologists call this response Romberg’s sign, and it signals sensory dysfunction. When patients have this kind of problem, they can’t feel the relationship between their body and their feet, so they must rely on visual cues to keep themselves upright. Without these cues, they lose their spatial orientation and fall.
I finished my examination. Before I could speak, Susan looked at me and said, “Dr. Pettinato, please help me walk again.” I assured her I would.
But I knew it was not going to be easy. The essence of neurology is localization: When I evaluate a patient I ask myself, is this a disease of the brain, spinal cord, nerve, or muscle? In Susan’s case, her decision-making skills as well as her speech, language, vision, hearing, coordination, and swallowing were normal, so I knew her illness did not involve the brain. Spinal cord? Symptoms of spinal-cord disease include numbness of the trunk, weakness, and bowel/bladder dysfunction. She showed none of these problems. Her strength was normal, so I felt confident that Susan did not have a myopathy, or muscle disease. Nerve problems were all that was left. Based on her symptoms and sensory deficits, I knew Susan had a neuropathy.
Sensation begins with the nerves in our limbs. Nerve impulses travel to the spinal cord, the brain, and then to the cortex for conscious appreciation. There are many causes of disruption in this pathway. A common cause is diabetes; uncommon causes include exposure to heavy metals, such as mercury, arsenic, and lead, as well as remote effects of cancer. But these are all diseases that progress slowly; Susan’s disease was moving quickly. I knew of several possible causes, but only one was likely: chronic inflammatory demyelinating polyneuropathy, or CIDP.
CIDP is an autoimmune disease. For unknown reasons, the immune system sometimes produces antibodies that mistakenly attack the body’s own tissues. In CIDP, antibodies strip the sheath that surrounds the nerve fibers. The loss of myelin slows or blocks the conduction of nerve impulses and leads to symptoms; if motor nerves are involved, the patient will develop weakness, and if sensory nerves are involved, as in Susan’s case, the patient will experience numbness and loss of sensation.
The exact number of patients with CIDP is not known, but in the United States the number probably exceeds 100,000. The disease can affect people of all ages, but the peak incidence occurs in the fifth and sixth decades of life. Although it can have an impact on different people in different ways, and spontaneous remissions can occur, CIDP tends to be associated with prolonged neurological disability, with roughly 20 percent of patients being confined to a wheelchair or bed.
Once CIDP is suspected, diagnosis is not very difficult. Blood tests will exclude systemic disorders, such as diabetes, as a cause. Radiographs can reveal the structural integrity of the spinal cord, but the diagnostic gold standard is a test called NCV, for nerve conduction velocity. NCVs are performed by electrically stimulating a nerve and measuring how fast the impulse is conducted. In CIDP, the conduction velocities are markedly slowed, a finding consistent with demyelination.
CIDP can be treated, but there is no cure. Corticosteroids and other immunosuppressive agents are helpful in modulating the immune response. Two potent and widely accepted therapies include intravenous immunoglobulin, which helps the body rid itself of the auto- antibodies, and plasma exchange, a process that literally filters antibodies out of the plasma. These expensive therapies usually have no adverse side effects and may be used in tandem if one doesn’t work by itself, particularly in severe cases of CIDP. In many instances both therapies must be repeated regularly to keep the immune response under control.
Susan’s blood work and radiographs were normal. Her NCVs showed markedly prolonged conduction times, so I knew I had the correct diagnosis. Her numbness, however, was getting worse, and the disease began to affect the nerves that control movement as well.
I was concerned that side effects from steroids might be too much for Susan to handle at her age. We agreed to try the intravenous immunoglobulin first. She handled it well, but the benefit was minimal. I tried plasma exchange next, but she didn’t tolerate the procedure, and much worse, her symptoms didn’t improve.
I was running out of options, and Susan was desperate. I felt her despair and knew I had to move quickly. Often a repeat treatment works, so I returned to the intravenous immunoglobulin. This time it was successful. Her symptoms stopped getting worse, and after several treatments, she slowly started to improve.
Susan has been receiving immunoglobulin treatments regularly, and although she isn’t cured, she is stable. The last time I saw her, I knew I’d kept my promise. When she left my office, she walked down the hallway without assistance.
John Pettinato is a neurologist in Concord, New Hampshire. The cases described in Vital Signs are true stories, but the authors have changed some details about the patients to protect their privacy.