• Sjögren’s syndrome
• sensory neuropathy

Sensory neuropathy with prominent ataxia reflecting kinesthetic sensory impairment is a well recognised form of neuropathy associated with Sjögren’s syndrome.^1–4 Pathologically, T cell invasion of dorsal root ganglia, loss of large sensory neurons, and secondary large fibre degeneration is seen in this neuropathy.⁴ However, a form of neuropathy associated with Sjögren’s syndrome, presenting with pain and superficial sensory involvement without sensory ataxia has been described anecdotally⁵ and in a case report.⁶ Clinicopathological details of the second form of neuropathy have not been elucidated. In this report we describe seven patients with Sjögren’s syndrome showing painful sensory neuropathy without sensory ataxia.

Patients studied were referred for painful neuropathy to Nagoya University Hospital and its affiliated institutions. All seven patients fulfilled diagnostic criteria for Sjögren’s syndrome by the American-European Consensus Group⁷ and showed painful peripheral neuropathy (table 1). Patients included six women and one man, ranging from 25 to 72 years old. In all patients initial symptom of neuropathy was paraesthesia or painful dysaesthesia in the most distal portions of the extremities, later extending proximally to involve the entire legs and arms. The trunk became involved in three patients, and the trigeminal nerve was impaired in three patients. Asymmetry in sensory impairment was present in four patients. None of the patients showed sensory ataxia in the initial phase. Most patients retained essentially normal muscle strength, but patient 1 showed slight weakness in distal limb muscles. Painful sensation was the most characteristic, and this symptom compromised activities of daily living in all patients. Superficial sensation for pinprick and temperature was prominently impaired. Deep sensation such as joint position and vibratory sense was substantially well preserved. Sensory ataxia and Romberg’s sign was not seen. Autonomic dysfunction was seen in four patients including Adie’s pupils, urinary disturbance, and loss of ¹²³I-MIBG cardiac accumulation; however, orthostatic hypotension was not present. Apparent hypohidrosis was seen in three patients. Thermal stimulation in two patients, resulted in absent sweating on the forehead, trunk, arms, and legs, with preserved sweat gland function on pirocarpine test. Thermography showed abnormal skin temperature gradient in four patients. Deep tendon reflexes were comparatively well preserved except in two patients. Motor nerve conduction studies showed no slowing (mean (SD) 52.3 (3.9) m/s in the median, 44.8 (6.1) m/s in the tibial nerves) and preserved compound muscle action potentials (CMAPs) (7.5 (3.5) mV in the median, 9.0 (6.3) mV in the tibial nerves). Sensory nerve conduction (50.1 (6.0) m/s in the median, 47.2 (10.4) m/s in the sural nerves) and sensory nerve action potentials (SNAPs) (13.6 (11.7) uV in the median and 9.0 (6.3) uV in the sural nerves) were generally well preserved; only in patient 4, SNAPs were not evoked. Somatosensory evoked potentials (SEPs) were also well preserved (mean (SD) 20.0 (1.1) ms at N20, 13.7 (1.2) ms at N13, and 9.3 (0.4) ms at N9).

Sural nerve biopsy in five patients showed a variable degree of myelinated fibre loss, predominantly affecting small diameter fibres (table 1, fig 1). Unmyelinated fibre density also was severely reduced. Axonal sprouting was essentially absent in all patients. In teased fibre preparations, degeneration was seen in 32% to 55% of axons, predominantly small diameter fibres. Vasculitis was not seen.

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Figure 1

(A) Transverse section of a sural nerve specimen from a control subject. (B) Specimen from a patient of painful sensory neuropathy with predominant small fibre loss associated with Sjögren’s syndrome (patient 1). Small diameter myelinated fibres are more noticeably involved and no axonal sprouting. Bars=25 μm.

Patient 2 developed sensory ataxia in the legs over the next nine years, and more details of this patient are given below. Patient 4 developed localised sensory ataxia in the fingers of the right hand over 11 years. Other patients showed persistent painful sensory neuropathy with gradual extension of distribution over 4 to 11 years of follow up.