MRI Shrimp Sign in Cerebellar Progressive Multifocal Leukoencephalopathy: Description and Validation of a Novel Observation.

BACKGROUND AND PURPOSE: There are no validated imaging criteria for the diagnosis of progressive multifocal leukoencephalopathy in the cerebellum. Here we introduce the MR imaging shrimp sign, a cerebellar white matter lesion identifiable in patients with cerebellar progressive multifocal leukoencephalopathy, and we evaluate its sensitivity and specificity. MATERIALS AND METHODS: We first identified patients with progressive multifocal leukoencephalopathy seen at Massachusetts General Hospital between 1998 and 2019 whose radiology reports included the term "cerebellum." Drawing on a priori knowledge, 2 investigators developed preliminary diagnostic criteria for the shrimp sign. These criteria were revised and validated in 2 successive stages by 4 additional blinded investigators. After defining the MR imaging shrimp sign, we assessed its sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: We identified 20 patients with cerebellar progressive multifocal leukoencephalopathy: 16 with definite progressive multifocal leukoencephalopathy (mean, 46.4 [SD, 9.2] years of age; 5 women), and 4 with possible progressive multifocal leukoencephalopathy (mean, 45.8 [SD, 8.5] years of age; 1 woman). We studied 40 disease controls (mean, 43.6 [SD, 21.0] years of age; 16 women) with conditions known to affect the cerebellar white matter. We defined the MR imaging shrimp sign as a T2- and FLAIR-hyperintense, T1-hypointense, discrete cerebellar white matter lesion abutting-but-sparing the dentate nucleus. MR imaging shrimp sign sensitivity was 0.85; specificity, 1; positive predictive value, 1; and negative predictive value, 0.93. The shrimp sign was also seen in fragile X-associated tremor ataxia syndrome, but radiographic and clinical features distinguished it from progressive multifocal leukoencephalopathy. CONCLUSIONS: In the right clinical context, the MR imaging shrimp sign has excellent sensitivity and specificity for cerebellar progressive multifocal leukoencephalopathy, providing a new radiologic marker of the disease.

Changes in MRS neuronal markers and T cell phenotypes observed during early HIV infection.

OBJECTIVE: To determine if changes in brain metabolites are observed during early HIV infection and correlate these changes with immunologic alterations. METHODS: Eight subjects with early HIV infection, 9 HIV-seronegative controls, and 10 chronically HIV-infected subjects without neurologic impairment underwent 1H magnetic resonance spectroscopy. Subjects with early stage infection were identified near the time of HIV seroconversion and imaged within 60 days of an evolving Western blot, while still having detectable plasma virus. Subjects had blood drawn for viral RNA and T cell quantification. RESULTS: Both N-acetylaspartate (NAA) and Glx (glutamate + glutamine) were decreased in the frontal cortical gray matter of seropositive subjects. NAA levels were found to be decreased in the centrum semiovale white matter of chronically HIV-infected subjects, but not in those with early infection. Both HIV-infected cohorts demonstrated a lower number of CD4+ T lymphocytes and a higher number of CD8+ T lymphocytes in their blood. Lower NAA levels in the frontal cortex of subjects with early infection were associated with an expansion of CD8+ T cells, especially effector CD8+ T cells. CONCLUSIONS: These results verify metabolism changes occurring in the brain early during HIV infection. Lower NAA and Glx levels in the cortical gray matter suggests that HIV causes neuronal dysfunction soon after infection, which correlates to the expansion of CD8+ T cells, specifically to an activated phenotype. Utilizing magnetic resonance spectroscopy to track NAA levels may provide important information on brain metabolic health while allowing better understanding of the virus-host interactions involved in CNS functional deficits.

Cerebral infarction in patients with AIDS.

PURPOSE: To establish the frequency, distribution, and pathogenesis of cerebral infarction as confirmed with MR imaging in a cohort of patients with acquired immunodeficiency syndrome (AIDS). METHODS: We reviewed all (71) abnormal cranial MR studies obtained at our institution in human immunodeficiency virus (HIV)-positive patients over a 2-year period and recorded the number and distribution of ischemic lesions, any associated abnormalities, and the MR angiographic findings, where available. Patients' charts were studied for relevant clinical data, biochemical and culture results, and potential etiologic factors. RESULTS: Twenty-two infarcts were seen in 13 of the 71 patients. Of these 22, the basal ganglia area was affected in 15, the middle cerebral artery territory in two, and the vertebrobasilar territory in five. Five patients had concomitant evidence of infection, six others used cocaine or were intravenous drug abusers. MR angiography was performed in eight patients; two of these had multiple lesions consistent with vasculitis, two had isolated lesions that corresponded with their parenchymal infarct, and four had normal findings. CONCLUSIONS: The frequency of infarction was 18%, higher than previously reported. The pathogenesis of infarction was multifactorial. Underlying infectious causes were identified in 39% of patients. Two patients had an idiopathic vasculitis.

Alpha Interferon in AIDS-Related Progressive Multifocal Leukoencephalopathy.

OBJECTIVE: To determine the efficacy of recombinant interferon alpha in the treatment of progressive multifocal leukoencephalopathy associated with the acquired immunodeficiency syndrome (AIDS). DESIGN: Open label, uncontrolled study. SETTING: Neurological unit and clinical AIDS program, Boston City Hospital, Boston, MA. PATIENTS: Four consecutive AIDS patients with pathologically confirmed progressive multifocal leukoencephalopathy. INTERVENTION: Each patient received alpha interferon for 4-12 weeks in a dose of 5-10 million units daily, administered subcutaneously. In addition, two of the four were taking acyclovir 2400 mg/day orally over the same period. RESULTS: None of the patients showed any clinical response to the therapy; the mean survival was 14 weeks. No adverse effects of the treatment were encountered. CONCLUSIONS: Despite anecdotal evidence that alpha interferon is effective in the treatment of progressive multifocal leukoencephalo pathy in non-AIDS patients, the experience of these patients suggests that the drug is of no benefit in AIDS-related PML.

Sciatic nerve entrapment in a child. Case report.

A child was brought for evaluation of signs of unilateral chronic progressive sciatic nerve dysfunction found to be due to nerve entrapment in the thigh by a fibrovascular band. Sectioning of the band was followed by marked improvement in the nerve function. Compression by a band is a rare but treatable cause of sciatic neuropathy.

A historic case of visual agnosia revisited after 40 years.

In one of the seminal works on visual agnosia, Adler (1944, 1950) presented the case of a 22-yr-old woman who sustained carbon monoxide cerebral toxicity in the Cocoanut Grove nightclub diaster of 1942. We located this patient 40 yrs after injury and performed a detailed reevaluation. The patient demonstrated persistent deficits in visual recognition, characterized most prominently by defective recognition of elemental shape and form, associated with alexia, prosopagnosia, visuospatial disorientation and impaired visual imagery. Visual acuity, colour recognition, writing ability and verbal intelligence were relatively preserved. Isolated bilateral occipital injury was demonstrated by CT and MRI scanning. On comparison with previously reported cases, our results support the hypothesis that carbon monoxide toxicity can induce a visual agnosia of the apperceptive type with well defined characteristics, seldom seen with other types of cerebral injury. Prognosis for long-term recovery is poor.

Reversible depression in Binswanger's disease.

The authors describe four elderly patients with Binswanger's disease in whom depression was prominent. Therapy with antidepressant drugs in three patients produced major improvement in psychological and physical functions. The one patient who could not be given an adequate course of antidepressant therapy because of intercurrent illness improved spontaneously after many months. The authors conclude that depression associated with Binswanger's disease is reversible despite persistence of neurological abnormalities. They speculate that this depressive syndrome is an example of organic affective disorder due to diffuse subcortical white matter ischemic lesions of the cerebral hemispheres and discuss the possible neuroanatomical basis of the depression.

Dizziness, falling, and fainting: differential diagnosis in the aged (Part II).

Salicylates used for rheumatoid arthritis, or in inadvertently high dosages by patients themselves, often cause toxicity manifested by tinnitus, hearing impairment, and imbalance. Vestibulotoxic drugs should always be considered in older patients when the cause of imbalance is not apparent. Gait disturbance is an important presenting symptom of subdural hematoma, along with a fluctuating level of alertness. A high degree of suspicion is required to diagnose this treatable condition early.

Dizziness, falling, and fainting: differential diagnosis in the aged (Part I).

Lack of awareness of benign positional vertigo is a common cause of misdiagnosis of dizziness. Patients complain of brief bouts of vertigo, specifically provoked by turning the head or by arising in the morning. The Bárány's test reproduces characteristic vertigo and nystagmus. Postural hypotension, by far the most common cause of recurrent dizziness and falls in the elderly, is especially notable on arising after prolonged bedrest. Vasoactive drugs are the most common culprits, typically antihypertensive agents, vasodilators used for angina, and tricyclic antidepressants.

Temporal arteritis-like presentation of carotid atherosclerosis.

A 68 year-old woman presented with a two-week history of amaurosis fugax, ipsilateral fronto-temporal headache and jaw claudication suggesting carotid giant cell arteritis. However, this syndrome proved to be due to atherosclerosis causing complete occlusion of the external carotid artery at its origin and narrowing of the internal carotid artery. Combined external and internal carotid endarterectomy relieved the symptoms. The symptom complex of temporal arteritis may be rarely mimicked by carotid atherosclerotic occlusive disease.

Universal dissociated anesthesia due to bilateral brain-stem infarcts.

A 59-year-old man had loss of pin-prick and temperature sensation over his head, face, neck, trunk, and all extremities while light touch, vibration, joint position sense, and deep pain were preserved. This was the cumulative result of infarctions in the territories of the right superior cerebellar and left posterior inferior cerebellar arteries that occurred three years apart. To our knowledge, a syndrome of bilateral discrete interruption of spinothalamic tracts and of the spinal tracts of the trigeminal system in the brain stem has not been reported. Dissociated sensory loss enveloping the entire body accompanied by truncal and limb ataxia without weakness demonstrated a striking clinical picture. The preservation of deep somatic and visceral pain when cutaneous pain sensation was lost was another notable feature. We review the causes of widespread dissociated sensory loss and discuss the implications of the dissociation of deep from superficial pain.

Tonic fecal seizures in nonketotic hyperglycemia of diabetes mellitus.

Three patients had recurrent focal motor seizures as the first manifestation of nonketotic hyperglycemia (NKHG) of diabetes mellitus. The seizures were characterized by stereotypical tonic changes in body posture and arrest of speech that have been associated with supplementary motor area seizures. Recognition of the link between this unusual form of focal epilepsy and NKHG would help in the early diagnosis and treatment of the serious underlying metabolic disturbance.

Anterior cervical arachnoid cyst simulating syringomyelia: a case with preceding posterior arachnoid cysts.

An arachnoid cyst lying anterior to the cervical cord at level C6-7 was found in a 28-year-old woman believed to have syringomyelia. This diagnosis was based both on previous findings at laminectomy and on computerized tomography. The diagnosis of arachnoid cyst was suspected because of clinical features atypical for classical syringomyelia and a history of arachnoid cysts found during childhood. Air myelography demonstrated an extramedullary intradural mass anteriorly that proved to be an arachnoid cyst. Drainage and subtotal resection resulted in marked clinical improvement. This case illustrates the need for reevaluation when a patient with "known" syringomyelia presents an atypical clinical picture. Anterior cervical arachnoid cyst, which may accompany or succeed posterior arachnoid cysts, should be considered.