Dr. Ho and Colleagues Reply

We thank Dr. Boylan for a very interesting perspective on our Clinical Case Conference, which described a patient with late-onset psychosis. This patient had no psychiatric history until age 60, when he developed paranoid delusions and auditory hallucinations. He has been followed for several years. He continues to meet the DSM-IV criteria for schizophrenia but not for psychosis secondary to a general medical condition or any other DSM-IV category. Repeated neuropsychological testing has not suggested dementia. Recently the patient was found to have a prostate nodule and an elevated prostate-specific antigen count; however, he has refused further workup. Dr. Boylan suggests that he may have paraneoplastic encephalomyelitis/sensory neuropathy on the basis of a neurological examination and a possibility of prostate cancer. Dr. Boylan presents an excellent brief review of the condition. As a result of her letter, the original three authors asked an independent neurologist (G.J.H.) to review the patient’s records for a neurological diagnosis. Unfortunately, the patient was unavailable for an examination or laboratory workup at this time.

Paraneoplastic neurologic syndromes are rare and occur at a rate of 1% or less (1; Dalmau et al., 1992). We believe that it is difficult to make a diagnosis of paraneoplastic encephalomyelitis/sensory neuropathy, which is characterized by the presence of small-cell lung cancer, along with clinical signs and symptoms of progressive dysfunction in various parts of the nervous system, including the cerebral hemispheres, brainstem, spinal cord, dorsal root ganglia, and nerve roots. It is believed that such dysfunction is a result of inflammatory changes associated with deposits of the anti-Hu antibody (Dalmau et al., 1992). Nonetheless, as Dr. Boylan points out, the clinical presentation of paraneoplastic encephalomyelitis/sensory neuropathy may vary considerably.

If our patient were to have paraneoplastic encephalomyelitis/sensory neuropathy, there could be two possible diagnoses. One possibility is that the entire clinical presentation, including late-onset psychosis, could be secondary to paraneoplastic encephalomyelitis/sensory neuropathy; alternatively, the patient may have late-onset schizophrenia along with paraneoplastic encephalomyelitis/sensory neuropathy. The first scenario is highly unlikely since the patient has not manifested signs of progressive encephalopathy over the follow-up period of several years. His clinical course has been remarkably similar to that of most patients with chronic paranoid schizophrenia. Although psychotic symptoms have been reported in paraneoplastic encephalomyelitis/sensory neuropathy, other symptoms of encephalopathy, such as dementia, confusion, and complex partial seizures, commonly accompany them (2, 3). The presence of a snout reflex, one of the so-called frontal release signs, is abnormal but is seen commonly in elderly individuals for a multiplicity of reasons, including accumulated frontal lacunar infarcts. As such, it is not pathognomonic of any specific neurological disorder. It is conceivable that our patient has late-onset schizophrenia along with paraneoplastic encephalomyelitis/sensory neuropathy secondary to a prostate neoplasm (4). Continued follow-up is necessary to rule out this possibility.

In sum, we think it is unlikely that our patient’s psychosis is secondary to paraneoplastic encephalomyelitis/sensory neuropathy given the lack of progressive neurological deficits over several years. Nonetheless, we will follow him closely and, with his permission, do a workup to rule out malignancy.